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Abstract

It is of great economic value to produce high-value PET-based MOF materials by the veritable elimination of waste PET, and provide sufficient MOF materials for hydrogen storage applications. Consequently, this work demonstrates the use of waste PET bottles as direct source of BDC acid linker during the synthesis of Cr-MOF. The PET-derived Cr-MOF materials showed even better textural and hydrogen storage properties than that from commercial BDC (Sigma–Aldrich).

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... In this context, MIL-53(Al) contains BDC (benzene 1,4-dicarboxylic acid) as a linker and aluminum ions as metal sites. Notably, the BDC linker can be successfully extracted from the household waste PET (water or beverage bottle), 8 while aluminum foil or an aluminum can (used for food packaging) can be a good source for aluminum ions (Al 3+ ). Hence, adopting this approach of utilizing waste for the large-scale production of MIL-53(Al) may offer an economically captivating solution for solid waste utilization. ...
... Hence, adopting this approach of utilizing waste for the large-scale production of MIL-53(Al) may offer an economically captivating solution for solid waste utilization. However, a few attempts have been made for the synthesis of MIL (Mateŕial Institut Lavoisier) series MOFs using household wastes such as PET bottles, 8,15 and a systematic way of producing large-scale MIL-53(Al) from PET and aluminum waste, and its potential application in selective CO 2 capture from gas mixture is rarely introduced in the academic curriculum. 8,15 Also, despite the widely recognized importance of MIL-53(Al), its synthesis and application are not commonly taught at the undergraduate level, and only a few literature reports are available describing the facile methodology for their synthesis to the students. ...
... However, a few attempts have been made for the synthesis of MIL (Mateŕial Institut Lavoisier) series MOFs using household wastes such as PET bottles, 8,15 and a systematic way of producing large-scale MIL-53(Al) from PET and aluminum waste, and its potential application in selective CO 2 capture from gas mixture is rarely introduced in the academic curriculum. 8,15 Also, despite the widely recognized importance of MIL-53(Al), its synthesis and application are not commonly taught at the undergraduate level, and only a few literature reports are available describing the facile methodology for their synthesis to the students. 16 It is worth mentioning here that MOFs of MIL series (MIL-101(Cr) and MIL-53(Al)) have shown a promising performance for CO 2 capture application, due to their high CO 2 adsorption capacity, prolonged thermochemical stability over repetitive adsorption−desorption cycles, and superior selectivity for CO 2 over other gases (N 2 , CH 4 , CO); therefore, facile synthesis of these MOFs is highly desirable. ...
Article
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To understand critical problems associated with solid waste and its consequences for the environment, a laboratory experiment is presented on the synthesis of aluminum-based metal–organic framework (MOF) MIL-53(Al) from household waste (PET bottles and aluminum foil/can), for undergraduate students of chemistry. This work is designed to teach students the research methodology and basic understanding of MOFs and their application in carbon capture and storage (CCS). Students also learnt several instrumentation techniques such as UV–vis spectroscopy, powder X-ray diffraction (P-XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and gas sorption to characterize the physicochemical properties of MIL-53(Al). The facile production of MIL-53(Al) enabled the students to investigate its applicability in CO2 sorption. The calculations of essential parameters such as CO2 over N2 selectivity and the use of statistical tools in data processing are also explained to the students. In the end, the instructor presented his/her feedback by evaluating the answer sheets (pre- and post lab work) and by demonstrating the overall lab work through a model presentation.
... 2 Of the various MOFs for energy storage devices, chromium (Cr)-based oxide networks are easy to fabricate and exhibit good chemical stability; however, they have not been extensively studied. Mateŕiaux de l′Institut Lavoisier (MIL)-101(Cr), which is a Cr-based MOF, has shown promising performance for diverse applications that include: (i) hydrogen storage 19,20 (ii) as an effective adsorbent for capture of gases such as CO, 21 CH 4,22 CO 2,23 and H 2 S, 24 and (iii) as a catalytic support for metal nanoparticles in catalytic reactions. 20 Ren and co-workers successfully performed large-scale, one-pot synthesis of MIL-101(Cr) with high reproducibility at low cost by direct use of waste poly(ethylene terephthalate) or PET as a source of terephthalic acid (TAP) and used environmentally friendly formic acid as the modulator. ...
... Mateŕiaux de l′Institut Lavoisier (MIL)-101(Cr), which is a Cr-based MOF, has shown promising performance for diverse applications that include: (i) hydrogen storage 19,20 (ii) as an effective adsorbent for capture of gases such as CO, 21 CH 4,22 CO 2,23 and H 2 S, 24 and (iii) as a catalytic support for metal nanoparticles in catalytic reactions. 20 Ren and co-workers successfully performed large-scale, one-pot synthesis of MIL-101(Cr) with high reproducibility at low cost by direct use of waste poly(ethylene terephthalate) or PET as a source of terephthalic acid (TAP) and used environmentally friendly formic acid as the modulator. They also simultaneously addressed the problem of recycling large amounts of PET waste. ...
... The PET-derived Cr-MOF products were found to have excellent textural properties with high hydrogen adsorption (storage) characteristics. 20 This MOF is known for its low density, high stability to moisture, thermal stability, unusually large pore volume and high effective surface area, and ample unsaturated active chromium sites. Some other aspects in favor of the use of the Cr-MOF include the following: (1) Cr (0.014%) has 1.55 times higher abundance compared to nickel (0.009%); 25 (2) nickel compounds are more toxic for humans as well as animals compared to chromium; 26 and (3) ease of synthesis of Cr-MOFs is comparable to that of Ni/Co-MOFs. ...
... Then the agglomerated particles get converted to oligomeric cluster molecules. Such clusters further initiate the development of metallic colloidal nanoparticles (Ren et al., 2016). The influence of certain surfactants exhibiting necessary functionalities (amines, thiols, alcohols, and acids) for creating possible interactions occluded along with particle substrates can enhance stable component growth and safeguards them from agglomeration, sedimentation, or else loss of in-built properties (Iavicoli et al., 2013). ...
... The quickest method of nanoparticle synthesis applied for silver, gold, platinum, and palladium in aqueous solution using microwave irradiation technique at an electric power of nearly 5060 Watts has been reported with the aid of red grape medium as a capping/reducing agent (Singh, 2018). This technique constitutes various advantages when compared with conventional heating: faster processing rate, enhanced purity, reduced heat loss, maximum heat efficiency, less quantity of waste generation, inexpensive process, and minimal chance of by-products formation (Ren et al., 2016). Solvent-free operations (dry medium) of such techniques are preferred to prevent quick and unconditional solvent heating leading to drastic explosions. ...
Article
Nanomaterial synthesis using a greener route has received massive attention as a sustainable, feasible, reliable, cost-effective, wealthy and environmentally friendly paradigm. Perhaps, synthesis via a greener route is considered as a sophisticated tool to minimize the toxic effects agglomerated with the conventional procedures of synthesis adapted for nanomaterials generally preferable in industry and laboratory. This work outlines the basic processes on the advanced patterns of the eco-friendly and various approaches involved in the green synthesis and its mechanism particularly accounted to metal and metal-based oxides like silver (Ag), gold (Au), zinc oxide (ZnO) and copper oxide (CuO) nanoparticles with the aid of plant extracts. This review article encompasses the essential purpose of biological approaches, green roué for nanoparticle synthesis, the impact of various operating parameters, and solvent-based techniques. The toxicity/stability of nanomaterials and the occluded surface engineering protocols for deriving biocompatibility along with various solvent systems have also been outlined. Various mechanisms involved for green synthesis, merits of greener chemistry and its application in various fields are emphasized. Finally, the prospects of green route strategies for metal/metal oxide nanomaterials synthesis are proposed for further development. The challenges in utilizing the green synthesized metal/metal oxide nanoparticles are discussed. The recommendations of the green chemistry towards the cleaner production are emphasized.
... Poly(ethylene terephthalate) (PET), one of the most extensively used non-biodegradable polymer materials associated with severe environmental problems throughout the world [30,31], was recently used as a cheap and sustainable source of the TPA 2− linker for direct synthesis of divalent metal-based MOFs including NTHU-2 (Zn) and [M 2 (TPA) 2 (DABCO) ] (M = Fe, Co, Ni, Cu, Zn) [32,33] as well as trivalent metal-based MOFs including MIL-47(V), MIL-53(Al, Ga, Cr) and MIL-101(Cr) [34][35][36]. This strategy could be one of the feasible solutions to speed up the industrialization process of MOFs by using low cost linker source [37]. ...
... The syntheses of divalent and trivalent metal-based MOFs based on PET were previously realised using DMF or water based protocols by replacing the TPA 2− linker with PET material [32][33][34][35][36]. However, when others followed a similar strategy in the presence of Zr(IV) salts, this did not lead to any crystalline MOF material [34]. ...
Article
We report here the direct synthesis of a zirconuim metal-based metal-organic framework (MOF) using waste poly(ethylene terephthalate) (PET) as ligand source. A Zr12 cluster terephthalate MOF hcp UiO-66 was derived via the reaction of ZrCl4 and PET in acetone and formic acid mixed solvent. The obtained material showed hexagonal prism shape with a good crystallinity and a much larger surface area than the theoretical value due to the ligand defects (≈3 missing linkers per Zr12 cluster). Besides, the resulting MOF exhibits both a high thermal stability in air and an excellent hydrothermal stability. Moreover, the hcp UiO-66 has been proven to be useful for the separation of benzene/cyclohexane due to a competitive adsorption process, as evidenced through mixed-vapor breakthrough experiments.
... MIL-101(Cr) has the empirical formula of [Cr3(O)X(BDC)3(H2O)2] (BDC = benzene-1,4-dicarboxylate, X = OH or F) with two types of internal cages with diameters of 29 and 34 Å, pore aperture window diameters of up to 16 Å, and Brunauer-Emmett-Teller (BET) surface area of 4000 m 2 /g [13]. Hydrated MIL-101(Cr) contains terminal water molecules that can be removed under a high vacuum and thus create possible Lewis acid sites linked to an octahedral trinuclear Cr(III)3O building system [14] to the dehydrated MIL-101(Cr). ...
... In the literature, MIL-101 (Cr) has been extensively investigated in an attempt to enhance its H2 uptake that has been recently reported to be 6.2 wt.% at 77 K, 80 bar, and BET surface area of 4100 m 2 /g [14,15]. ...
... Huang et al. [198] established a sustainable procurement procedure for MOF linkers by synthesizing luminescent nano-porous zinc phosphates directly from poly (ethylene)terephthalate (PET) plastic bottle waste as a source of linker terephthalic acid (BDC). Cr-MOF has also been fabricated using waste PET (as a linker) and formic acid (as a modulator) [199]. Moreover, PET waste as a linker has been also employed for synthesis of MIL-family MOFs (MIL-101, MIL-53, and MIL-47) under hydrothermal conditions [200,201]. ...
... Significant research efforts have been devoted to development of green MOFs for gas storage, especially H 2 storage, which is considered the greenest fuel option. A sustainable biomassbased approach has been developed for synthesis of MIL-101(Cr), in which a terephthalic acid (BDC) linker was extracted directly from large quantities of PET waste [199]. The synthesized MOF exhibited unique textural properties and the potential to adsorb H 2 . ...
Article
Sustainable methods of synthesizing metal–organic frameworks (MOFs) are of paramount importance to energy conservation efforts and environmental remediation. It can be a significant tool in the global campaign to avoid use of hazardous substances, such as metal ions, organic solvents, and complexes in metal–organic chemistry. MOFs with porosity and crystalline nature offer structural tunability via variation in metal node and organic linker that promote their wide applicability at both scientific and industrial level. Besides fascinating properties of MOFs, their real field applications are still limited due to adverse environmental impact of the conventional synthesis approaches. Considerable research efforts have been devoted to devising clean and sustainable synthesis routes for MOFs to reduce the environmental impact of their preparation. This review covers the design strategies for greener, more energy-efficient, and less-toxic MOF synthesis through application of 12 green chemistry principles. Attention is given to development of green and industrially acceptable MOF chemistry based on (i) safer solvent/or reaction media, (ii) sustainable metal ions, and (iii) biocompatible (i.e., biomolecule/biomass-derived) organic linkers. The versatile functionality, biodegradability, biocompatible nature, and high drug loading capacity of green MOFs are highly promising for environmental and medical applications. In this review, the recent update on applicability of green MOFs in catalysis, adsorption/separation processes, and therapeutics is highlighted. In the last section, outlook and future challenges are illustrated, keeping in view their disposal and health related concerns.
... Polyethylene teraphthalate (PET) is the most commonly used plastic, which finds its application in repositories for liquids and foods due to its low price, transparency, and sufficient mechanical performance. The approximate amount of PET products consumed exceeds 24 million per year, and the amount proceeds to grow [15], contributing a significant volume of plastic waste. Consequently, new technologies to utilize PET wastes are in high demand to maximize recycling and avoid landfilling or incineration. ...
... The higher amounts of conventional blowing agent (15,25, and 29 pbw) and water (2.5, 3.0, and 3.5 pbw) increase the expansion efficiency of the foam, resulting in product structures with~2 times larger cells and products with an apparent density of~30 kg/m 3 . ...
Article
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Currently, polyurethane foam producers come across the several problems when petroleum-based polyols are replaced with low functionality biomass, or waste-based, polyols. In addition, the dilemma is intensified with regulations that require full or partial replacement of blowing agents that can cause high ozone depletion with alternatives like water, which causes the formation of CO2. Therefore, these gases diffuse out of the foam so quickly that the polymeric cell walls cannot withstand the pressure, consequently causing huge dimensional changes at ambient temperature and humidity. Even though the theoretical stoichiometric balance is correct, the reality shows that it is not enough. Therefore, polyethylene terephthalate waste-based polyol was chosen as a low functionality polyol which was modified with high functionality sucrose-based polyol in order to obtain dimensionally stable polyurethane foams in the density range of 30–40 kg/m3. These more stable foams are characterized by linear changes no higher than 0.5%, short-term water absorption by partial immersion no higher than 0.35 kg/m2, and water vapor resistance factors up to 50. In order to obtain thermally efficient polyurethane foams, conventional blowing agents and water systems were implemented, thus, assuring thermal conductivity values in the range of 0.0198–0.0204 W/(m·K) and obtaining products which conform to all the requirements for performance of sprayed and factory-made polyurethane foam standards EN 14315-1 and EN 13165.
... The methods used for hydrolysis include microwave heating (Liu et al. 2005). In the last years, some ways to obtain BDC from PET have been reported, e.g., those from Manju et al. (2013), Deleu et al. (2016), and Ren et al. (2016). Deleu et al. (2016) reported a pre-treatment of PET bottles, including a trituration and sieving step, followed by a ballmilling process with liquid nitrogen for 90 min to obtain a PET powder that was then heated at 200 °C by microwave to perform the polymer hydrolysis. ...
... Deleu et al. (2016) reported a pre-treatment of PET bottles, including a trituration and sieving step, followed by a ballmilling process with liquid nitrogen for 90 min to obtain a PET powder that was then heated at 200 °C by microwave to perform the polymer hydrolysis. On the other hand, Ren et al. (2016) reported the depolymerization of PET pieces by employing a mixture of water-ethylene glycol as the solvent heated in a high-pressure Berghof reactor, at 210 °C, for 8 h. Although these methods are known, they often require sample pre-treatments, which are time and resource-consuming. ...
Article
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In this work, we present the preparation of MOF-5 using terephthalic acid as a ligand obtained from polyethylene terephthalate waste. The results showed that the obtained terephthalic acid gave similar features to the commercial one. The synthesized MOF was fully characterized and tested for CO2 adsorption at 35 °C and at atmospheric pressure, under static and dynamic conditions, presenting adsorption capacities of 2.5 and 2 mmol g−1, respectively, which are higher than the reported values. At 1000 kPa, in static conditions, the adsorption capacity was 7.8 mmol g−1. The obtained results demonstrated that this MOF presented improved structural stability and CO2 adsorption capacity compared with the results reported elsewhere.
... Al-MOF, Ni-Mn MOF etc.). At the same time, PET can also be used for the preparation of MOF catalysts (MOF methane dry reforming catalyst) in a sustainable manner (Karam et al., 2021) as well as the green synthesis of MOFs for hydrogen storage from PET bottles (Ren et al., 2016). Jamil et al. (2020) also investigated the use of MOF catalysts for the production of biodiesel from wasted cooking oil implementing the key components which constitute the CE logic (D'Adamo, 2019;D'Adamo et al., 2021;Symeonides et al., 2019). ...
Article
A zinc-based Metal-Organic Framework (MOF) has been prepared by utilizing adipic acid as an aliphatic ditopic linker via both solvothermal and sonochemical methods. The ultrasound irradiation has reduced the reaction time and has led to smaller particle size. The samples were evaluated for their catalytic efficiency by the electrochemical reduction of CO2, with carbon monoxide and hydrogen being the sole products. At lower potentials (−1.5 V to −1.7 V) the ultrasound sample achieved up to 10% better faradaic efficiency towards CO (FECO). At more negative potentials (−1.8 V to −1.9 V) the FECO of the two samples start to equalize to a maximum of around 58%. The proposed work contributes to circular economy and the results may be useful for further investigation of the opportunities created by the usage of MOFs in the framework of energy recovery and efficiency, waste reduction, responsible consumption of raw materials and natural resources as well as the potential introduction of MOF to Circular Economy and cost-efficient transition to a “green” and sustainable industry.
... Fig. 1 shows synthesis process (Fig. 1a) and XRD patterns (Fig. 1b-d) of assynthesized MOFs. The recorded patterns of BDC-based MOFs exhibit sharp peaks that match previous reports [3,[24][25][26][27], demonstrated the successful synthesis of these MOFs (Fig. 1b). The sodalite structures of ZIF-8 and ZIF-67 are identified by the XRD spectra with sharp peaks [28]. ...
Article
Metal-organic frameworks (MOFs) have been widely used to improve fire safeties of polymers as burgeoning flame retardants. There is no report about the influence of MOFs' compositions on enhancing fire safety of polymers. This work synthesized 9 pristine MOFs, including 3 MOFs with 1,3,5-tricarboxylic acid as organic ligands, which were added into polystyrene and epoxy resin, respectively. To deeply investigate impacts of MOFs' components, heat release, smoke emission and CO production behaviors were detected during the combustion processes of polymer/MOFs. It is clear that cobalt-based MOFs had better flame-retardant performance than other MOFs with same organic ligands. While the influence of organic ligands is irregular, affected by corresponding metallic components. The type of polymers also affects flame-retardant performance of MOFs. This work systematically analyzed the influence of MOFs' components on performance of polymer composites, which provides guidelines and database for further application of MOFs as flame retardants.
... This has made researchers and environmentalists to find appropriate disposal ways, and also safer and economic solutions to overcome this environmental problem. Since this issue has attracted many researchers' attention, different recovery methods like primary recycling, mechanical recovery, chemical recovery, energy recovery (incineration) and biological recycling have been developed for polymer waste recycling [1,[4][5][6][7] and restoring them to high-value products [8][9][10][11][12][13][14]. ...
Article
Full-text available
Polyethylene terephthalate (PET) recycling is investigated in this work. PET is a polymer in which hydrolytic degradation of polymeric chains occurs during thermomechanical reprocessing. This kind of processing yields poor melt strength and low viscosity for recycled polyethylene terephthalate (RPET). The chain extension effect of pyromellitic dianhydride (PMDA) on phase morphology and crystallinity of the RPET and polyethylene vinyl acetate (EVA) blends is verified or the first time including crystallization, thermal behavior and morphologies of the blended samples. First, RPET/EVA blends were prepared with 90/10, 70/30 and 60/40 weight ratio in an internal mixer. Pure RPET and virgin PET (VPET) were also reprocessed for comparison. Samples of RPET/EVA, VPET/EVA, RPET/EVA/PMDA and VPET/EVA/PMDA were examined using RPET (or VPET)/EVA = 60/40 (w/w) and 0.5% for PMDA. Both XRD and DSC tests revealed that PMDA and EVA reduce the rate and degree of crystallinity in PET, however, PMDA and PET increase both rate and degree of crystallinity in EVA. SEM images also illustrated RPET/EVA blend to be in co-continuous morphology while adding 0.5 wt% PMDA to the blend changes the structure to microfibrillar matrix-disperse state.
... On the other hand, one way to reduce the overall expense on MOF synthesis is to use cheaper ligand sources. For example, the commonly used terephthalic acid linker can be derived from the depolymerization of waste polyethylene terephthalate bottles as an alternative (Ren et al., 2016;Lo et al., 2016). Not only this approach is an economically attractive strategy for large-scale MOF synthesis, but this would also save a significant portion of polyethylene terephthalate wastes from going to landfills. ...
Thesis
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The widespread usage of organic chemicals has led to an unprecedented level of pollution and associated health risk concerns. Although activated carbon (AC) based adsorption is commonly used in wastewater treatment and air purification processes, now, new metal-organic frameworks (MOFs) adsorbents with superior surface areas, chemically tuneable structures, and excellent reusability are available. This thesis evaluates the application of selected MOFs and their modified variants for removing organic pollutants from aqueous and humid air streams, reporting adsorption capacity and kinetics. For the removal of aqueous phase pollutant 2-chlorophenol, the higher surface area of MIL-101 (Cr) even with improved surface amination, gave inferior adsorption capacity compared to the hydrophobic AC, indicating the importance of MOF’s hydrophobicity. A hydrophobic MIL-101 (Cr) was synthesized using a PDMS vapour coating protocol, creating a new material with the same surface area and pore volume as pristine MIL-101 (Cr). For 0.5% toluene P/P0 vapour co-adsorption at 40% RH, this composite showed a 60% higher uptake capacity and a 34% higher aggregate adsorption rate compared to pristine MIL-101 (Cr), and 360% faster kinetics relative to AC. A solution-based treatment for MIL-100 (Fe) was developed using calixarene, producing super hydrophobic surfaces, which at 40% RH and 0.5% toluene P/P0, exhibited a 68% higher aggregate uptake rate, despite having lower pore volumes and surface areas. Finally, MIL-96 (Al) was modified using hydrolysed polyacrylamide polymer, which enlarged the 3.2-μm particles by 225% and transformed their crystal morphology. The polymer also contains amide with NH2 moieties which improved the modified MIL-96 (Al)’s uptake capacity of perfluorooctanoic acid. Overall, this thesis highlights the complexity of co-adsorption when hydrophobic and hydrophilic adsorbates are both present. It also recalls the importance of adsorption kinetics, in contrast with current MOF research emphases, which are on surface area and adsorption capacity. Faster adsorption kinetics may be preferred over a slow-diffusing adsorbate, even if the final uptake capacity is superior, for some industrial applications.
... The main issues of these materials remain their synthesis, generally at the gram scale, and the final price of the materials. Recently, these materials have been produced using commercial depolymerized PET as a source of organic ligands to build various MOFs, based on Zr [10,11], Cu [12], Zn [13], Cr [14,15], Al [14,16], Ga [14], and V [16], with a high purity. We have recently proposed the use of LiB waste as a source of metal ions for the synthesis of such materials [17][18][19]. ...
Article
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This paper reports a simple method to recycle plastic-bottle and Li-ion-battery waste in one process by forming valuable coordination polymers (metal–organic frameworks, MOFs). Poly(ethylene terephthalate) from plastic bottles was depolymerized to produce an organic ligand source (terephthalate), and Li-ion batteries were dissolved as a source of metals. By mixing both dissolution solutions together, selective precipitation of an Al-based MOF, known as MIL-53 in the literature, was observed. This material can be recovered in large quantities from waste and presents similar properties of purity and porosity to as-synthesis MIL-53. This work illustrates the opportunity to form hybrid porous materials by combining different waste streams, laying the foundations for an achievable integrated circular economy from different waste cycle treatments (for batteries and plastics).
... Terephthalic acid is a common linker for MOF materials, which is usually produced from p-xylene. Ren et al. utilized the similar reaction conditions of poly(ethylene terephthalate) (PET) hydrolysis and MOF synthesis [109]. In their approach, waste PET bottles were used as direct source of terephthalic acid linker during the synthesis of Cr-MOF. ...
... For example, in PET research, one of the advances has been an attempt to convert PET into MOFs by applying two-step methods involving conversion of waste PET into H 2 BDC, which is, in turn, used for the synthesis of MOFs like Cr-MOFs, MIL-47, or UiO-66. [25][26][27][28] However, the separated depolymerization and synthesis processes have been shown to be energy-as well as time-consuming. To bypass these obstacles, other investigators have made use of direct conversion of PET into trivalent MOFs (e.g., MIL-47, MIL-53, and MIL-101, etc.) or pillared-paddlewheel MOFs [e.g., M 2 (BDC) 2 (DABCO)] with the addition of HF, HCl, formic acid, or NaOH, under hydrothermal conditions. ...
Article
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Polyester plastics such as poly(ethylene terephthalate) (PET) are utilized commonly in everyday life, yet only a small portion of these plastics are recycled, and typically, the recycling procedures face energy or pollution problems. Accordingly, methods that could convert waste polyester plastics into value-added products like metal–organic frameworks (MOFs) are desirable. For the first time, we report a general and versatile polyoxometalate-based plastic hydrolysis protocol for one-pot syntheses of polyoxometalate-based metal–organic frameworks (POMOFs). We show that this protocol could be applied to diverse kinds of plastics [i.e., PET and poly(butylene terephthalate)] and various polyoxometalate systems (i.e., Ni 6PW 9, Zn 4PMo 12, and V 6S) to generate POMOFs (i.e., Ni-POMOF, Z-POMOF, and VMOP-11) with ∼100% hydrolysis efficiency. Besides, this method could be easily scaled up, and the large-scale POMOFs obtained could efficiently catalyze the syntheses of cyclic carbonates in simulated flue gas from a coal-fired power plant. Thus, our approach of polyester plastic hydrolysis into valuable, eco-friendly, and biodegradable POMOFs sheds light on the development of novel techniques in waste-plastic recycling.
... 6H 2 O in a Berghof high-pressure reactor(figure 5) in water medium at 210°C for 8 h and recommended as a hydrogen-storage material[94].An Al-MOF 'Al-MIL-68-Mes' (figure 6), containing small trigonal and large hexagonal channels, having high specific surface area 1040 m 2 g −1 , chemical composition [Al(OH)(O 2 C-C 3 H 4 -CO 2 )] · nH 2 O and derived from mesaconic acid (methylfumaric acid H 2 Mes), was prepared from mesaconic acid, NaOH and Al 2 (SO 4 ) 3 · 18H 2 O in mild conditions at 95°C in water for 45 min under MW[92]. The formed MOF exhibited a considerable chemical and thermal (350°C) stability. ...
Article
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Modern trends in the greener synthesis and fabrication of inorganic, organic and coordination compounds, materials, nanomaterials, hybrids and nanocomposites are discussed. Green chemistry deals with synthesis procedures according to its classic 12 principles, contributing to the sustainability of chemical processes, energy savings, lesser toxicity of reagents and final products, lesser damage to the environment and human health, decreasing the risk of global overheating, and more rational use of natural resources and agricultural wastes. Greener techniques have been applied to synthesize both well-known chemical compounds by more sustainable routes and completely new materials. A range of nanosized materials and composites can be produced by greener routes, including nanoparticles of metals, non-metals, their oxides and salts, aerogels or quantum dots. At the same time, such classic materials as cement, ceramics, adsorbents, polymers, bioplastics and biocomposites can be improved or obtained by cleaner processes. Several non-contaminating physical methods, such as microwave heating, ultrasound-assisted and hydrothermal processes or ball milling, frequently in combination with the use of natural precursors, are of major importance in the greener synthesis, as well as solventless and biosynthesis techniques. Non-hazardous solvents including ionic liquids, use of plant extracts, fungi, yeasts, bacteria and viruses are also discussed in relation with materials fabrication. Availability, necessity and profitability of scaling up green processes are discussed.
... Modified chromium-based Metal Organic Frameworks (MOF) such as Cr-MIL-PMIDA are regarded as highly efficient adsorbents for the removal of REE from aqueous solutions (Ren et al., 2016;Lee et al., 2018). High stability, large pore area and ability for modification with functional groups make the recovery of REE economically feasible. ...
Article
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Acid mine drainage (AMD) contains an array of valuable resources such as Rare Earth Elements (REE) and Copper (Cu) which can be recovered along with fresh water. Low pressure nanofiltration with NF90 membrane was first studied to recover fresh water from synthetic AMD and concentration of dissolved metals for subsequent efficient selective recovery. Organic matter (OM) present in AMD was found to cause membrane fouling which resulted in significant flux decline. Powdered eggshell was investigated as a low-cost adsorbent for OM removal. The study showed that a 0.2 mg/l dose of powdered eggshell adsorbed 100% of OM and Fe with no significant loss of other dissolved metals. A steady permeate flux of 15.5 ± 0.2 L/m²h (LMH) was achieved for pre-treated AMD with a solute rejection rate of more than 98%. A chromium-based metal organic framework (MOF) modified with N- (phosphonomethyl) iminodiacetic acid (PMIDA) and an amine-grafted mesoporous silica (SBA15) material was synthesized for selective recovery of REE and Cu, respectively. The two adsorbents were used sequentially to selectively adsorb REE (91%) and Cu (90%) from pH adjusted concentrated feed. The formation of coordinating complexes with carboxylate and phosphonic groups on MOF was found to be the primary driving force for selective REE adsorption. Selective uptake of Cu onto amine-grafted SBA15 was due to the formation of strong chelating bonds between Cu and amine ligands. Both adsorbents remained structurally stable over 5 regeneration cycles. The findings here highlight the practical potential of membrane/adsorption hybrid systems for water and valuable metal (REE) recovery from AMD.
... Second important substrate used in CoOF synthesis is organic ligand-terephthalic acid. As reported by Huang et al. [75] and Ren et al. [76], linker can be recovered from the PET waste, by hydrolysis and reused for synthesis of NTHU-2, NTHU-3, MOF-5, MIL-53, MIL-101, and chromium-based MOF. The syntheses of MOF structures from the recycled terephthalic acid were confirmed by Deleu et al. [77]. ...
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... For example; Ren et al. reported a Cr-MOF from polyethylene terephthalate bottle wastes via green synthesis and used it for hydrogen storage. 35 42 Grall et al. reported a mesoporous Cr-MOF for in vitro biocompatibility nanocarrier applications. 28 In this article, to the first date, novel Cr(III)-MOF-NPs were synthesized and fully characterized via numerous microanalytical and spectral tools. ...
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The entire world is facing with a severe dilemma of water pollution which is mainly concerned with the chemical and biological contaminants that have endangered the quality of drinking water. The Membrane separation technology is vastly acknowledged as an advanced process for water filtration and purification, having the potential to alleviate global matter of contention of freshwater scarcity. Various nanofillers have been used by many in water purification. This methodology has been accepted as feasible and active to produce a multifunctional nanocomposite membrane i.e. membranes with higher performance along with their synergistic effects of organic polymer matrix and inorganic nanomaterials for water and wastewater treatment. Recently, inorganic nanofillers such as inorganic metal oxides (SiO2, TiO2, ZnO, Ag, etc.), carbon based (CNT, GO) and mixed nanoparticles (SiO2-TiO2, GO-TiO2, GO-SiO2, etc.) have been extensively used to prepare polyvinylidene fluoride (PVDF) nanocomposite membranes with desired properties for water purification. This review aims to highlight the performance of nanofiller incorporated PVDF membranes and the novel strategies explored for fabrication of the PVDF nanocomposite membrane to cater to the current requirements and expectations of water purification performances.
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In this work, which was based on the concepts of green chemistry, polyethylene terephthalate (PET) waste bottles were employed as the source of a benzene-1,4-dicarboxylate linker for the synthesis of MIL-53(Cr). Subsequently, the synthesized MIL-53(Cr) was characterized and employed for the first time as a stationary phase for the HPLC determinations of different methylxanthines in black, green, and white tea samples, respectively. As observed, the main working mechanism was the reversed-phase; however, size-exclusion effects were noticeable on catechins, which exceeded the dynamic diameter of MIL-53(Cr) (∼8.5 Å). Under optimal conditions, the MIL-53(Cr) column exhibited the best efficiency for caffeine with 35,300 plates m⁻¹ and a chromatographic resolution of ≥1.72 for all the detected compounds in the tea samples. The developed method was linear (0.183–200 μg mL⁻¹) and the obtained LOD values were 0.055–0.072 μg mL⁻¹. The obtained RSDs, which were determined employing different chromatographic parameters indicated the feasible reproducibility of the columns and verified the ruggedness of the method. The results confirmed that the methylxanthine contents of the black teas were the highest (51.28–60.02 mg per tea bag; 2.0 g), followed by those of the green teas (26.72–43.68 mg per tea bag), before those of the white teas (20.44–25.36 mg per tea bag). Furthermore, the separation performances of the MIL-53(Cr) column and two silica-based C18 commercially columns (3 and 5 μm-sized particles) were compared. The structure of the MIL-53(Cr) afforded higher retention factors in the methylxanthines because of the hydrophobic π–π interactions between the solutes and aromatic ring of the organic linker. Conclusively, the MIL-53(Cr) column, which was prepared from PET bottles, could be applied to the routine analyses of methylxanthines in tea samples.
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Sustainable recycling and safe disposal of waste polyethylene terephthalate (PET) are growing concerns worldwide. We have synthesized green fluorescent carbon nanodots (CDs) utilizing waste PET bottles as carbon precursors following a greener solvothermal synthetic route in this work. The obtained CDs (∼6 nm) exhibited excellent photoluminescence properties and displayed high selectivity for lead ions (Pb2+) through a fluorescence quenching effect. Besides, the CDs possessed a highly negative zeta potential value of -40 mV, which suggests good colloidal stability of the nanosuspension. The synthesized optical nanosensor demonstrated excellent anti-interference activity for Pb2+ detection despite the presence of co-existing cations or anions. The calculated low detection limit of ∼21 nM and fast response time of the synthesized nanoprobe displayed its significant potential in trace level detection of Pb2+ ions from the aqueous medium. Furthermore, the synthesized CDs proved their excellent practicality in sensing Pb2+ ions from actual water samples. Therefore, the present work's findings illustrate the CDs as a promising fluorogenic probe for environmentally benign and cost-effective detection of Pb2+ ions from aqueous solutions. © 2021 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
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A new Sn(II)-based metal-organic framework (MOF) has been solvothermally synthesized using post-consumer waste PET bottles as an organic linker source. The potential of the Sn(II)-MOF as an adsorbent material in the removal of arsenate (AsO4³⁻) and phosphate (PO4³⁻) from the aqueous medium was examined. The adsorption kinetics of the target anions followed the pseudo-second-order kinetic model, and the Langmuir isotherm best describes the adsorption profile. The adsorbent displayed a significant adsorption capacity of 90.90 mg g⁻¹ and 126.58 mg g⁻¹ for AsO4³⁻ and PO43−, respectively. The synthesized Sn(II)-MOF demonstrated promising anti-interference activity in the presence of co-existing anions, mainly F⁻, Cl⁻, NO3−, and SO4²⁻. Besides, the synthesized Sn(II)-MOF exhibited remarkable removal efficiency (~99%) of AsO4³⁻ from actual water samples viz. tap water and lake water. Further, the work elucidates the role of surface charge regulation where the positively charged Sn(II)-MOF is converted to negatively charged tin oxide nanoparticles (SnO2 NPs) via a simple thermal decomposition route. The MOF derived highly crystalline SnO2 NPs (~25 nm) were explored in the adsorptive removal of toxic manganese (Mn²⁺) ions. The synthesized SnO2 NPs displayed excellent Mn²⁺ adsorption capacity (qm) of 52.63 mg g-1, which is in good agreement with the experimental value (qexp) of 56.96 mg g⁻¹. Moreover, the SnO2 NPs displayed remarkable selectivity in Mn²⁺ adsorption despite the presence of other cations/anions. Notably, the present work can prove to be an economically viable method of recycling waste PET bottle into value-added adsorbent material for the decontamination of water.
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Polyethylene terephthalate (PET), a chemically stable polyester with multiple applications has risen dramatically in manufacturing and consumption in the past decades. The increase in PET use has resulted in considerable volumes of waste PET pilling up and thus causing increased health and environmental concerns. Apart from the landfills and incineration solutions, the common waste PET recycling practices mainly focus on low value downstream products. All the above mentioned factors have contributed to the lower waste PET recycling overall rate of less than 30%, and created a need for alternative treatment options. Our earlier work has proven the feasibility for converting clear PET bottles into high value-added metal-organic frameworks (MOFs) materials. The feedback from industries indicated that the colourful PET bottles and food trays are currently considered problematic to be recycled economically. In response, this work focuses on the use of various types of PET wastes as sources of benzene dicarboxylic acid (BDC) linker for the synthesis of the zirconium-based MOF UiO-66(Zr). The BDC linker was extracted from food trays, green bottles, brown bottles and PETCO beads through glycolysis (depolymerization). Post synthesis characterization revealed that textural properties of the waste PET-derived UiO-66(Zr) MOFs were comparable to those of the MOFs derived from commercial chemicals as exemplified in the SEM images and XRD patterns. The diffraction pattern peaks typically observed for commercial grade BDC positioned at 2θ= 17.21, 25.01 and 27.64°, were observed for the PET-derived BDC samples, confirming the crystalline nature of samples. However, The MOFs synthesized from BDC derived from green and brown Pet bottles measured lower BET surface areas in the range of 933-1085 m2/g compared to 1368 m2/g for MOFs synthesized from commercial BDC linker. This phenomena is attributed to the presence of organic dyes contained in the coloured PET bottles residing in the MOFs pores. This was further confirmed by the infrared spectra of the post-consumer PET derived BDC showing a peak at 3158 cm−1 assigned to amine N-H functional group, as well as the much stronger =C-H bend. This study complements the business case development model of ‘Waste PET to value-added MOFs’. Keywords: Metal-organic framework, Benzene dicarboxylic acid , PET waste, UiO-66(Zr).
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The reaction of post-consumer poly(ethylene terephthalate) (PET) with waste of battery acid (sulfuric acid solution as 7.8M determine by chemical titration) was investigated in terms of temperature, and time at particle size about 2mm. The reaction extent reached 80% in four days at 100°C and 90% in 5 hours at 132°C (boiling point of waste of battery acid solution). Terephthalic acid (TPA) obtained was purified and considered in the same level of quality of the commercial. It was concluded that the hydrolysis occurred preferentially at the chain ends and superficially, having as controller mechanism the acid diffusion into the polymer structure.
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Nanoscale MIL-101 has been controlled synthesized by a seeding method, and further used as the support for immobilizing RhNi nanoparticles (NPs) as efficient catalysts toward hydrogen generation from hydrous hydrazine in alkaline solution. Compared with other commercial materials and bulk MIL-101, RhNi NPs supported on nanoscale MIL-101 exhibit the highest catalytic activity and 100% hydrogen selectivity.
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The physical upper limit of hydrogen uptake for powder and compressed pellet MIL-101 has been experimentally investigated. Maximum uptake in pellets at 20 K achieves 9.6 wt% and 42 g L-1. Moreover, cryo-adsorption of hydrogen on pellets compared to liquid H2 possesses a larger temperature window for operation without boil-off loss, which will be beneficial for industrial applications.
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The recycling of post-consumer PET (POSTC-PET) as a technology is a cross-disciplinary practice with many fields of science involved. These include polymer chemistry and physics, process engineering and manufacturing engineering. This paper presents a concise background of the current state of knowledge with respect to POSTC-PET recycling covering the disciplines mentioned above. In the first section of this paper, a brief background is presented about virgin PET synthesis, thermal transitions, processing and applications. The second section covers the PET recycling process with a focus on contamination and ways to increase the molecular weight of recycled PET (R-PET). It serves as an introduction to Section 3 where the chain extension process is described in detail. In Section 3, the current understanding of chain extenders, chain extension experimentation variables and equipment is reviewed. Reactive extrusion process is described in Section 4 with a special focus on system stability under chain extension conditions. Section 5 covers the effect of chain extension on R-PET thermal transitions and crystallinity. Section 6 presents the injection stretch blow moulding (ISBM) process as a possible application for R-PET with a focus on preform and bottle moulding. The last section gives a description of FT-IR technology to detect bottles’ orientation and conformation changes.
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Nanoparticles of MIL-101(Cr) have been fabricated using a hydrothermal method for the first time. The particle size can be controlled from 19 (4) nm to 84 (12) nm, by using a monocarboxylic acid as a mediator. These nano MIL-101(Cr) materials exhibit higher selectivities for CO2 over N-2 than bulk MIL-101(Cr).
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We combined targeted chemistry and computational design to create a crystal structure for porous chromium terephthalate, MIL-101, withverylargeporesizes and surface area. Its zeotype cubic structure has a giant cell volume (∼702,000 cubic angstroms), a hierarchy of extra-large pore sizes (∼30 to 34 angstroms), and a Langmuir surface area for N2 of ∼5900 ± 300 square meters per gram. Beside the usual properties of porous compounds, this solid has potential as a nanomold for monodisperse nanomaterials, as illustrated here by the incorporation of Keggin polyanions within the cages.
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PET contains up to 85 wt% of terephthalic acid (BDC), but has never directly been used as a source of organic linker for MOF synthesis. By combining metal salts and PET under hydrothermal conditions in a microwave oven, PET hydrolysis and MOF synthesis occur simultaneously. With this one-pot reaction, MIL-53(Al) and MIL-47(V) have been successfully synthesized. Optimization of reaction and calcination conditions for MIL-53(Al) results in phase-pure MOF with a BET surface of 1481 m?/g. When the hydrolysis is done as a separate first step, less stable MOFs like MIL-88B(Fe) can be synthesized by adding the metal salt and methanol to the hydrolyzed mixture in a second step. By partially depolymerizing the surface of PET bottles it is possible to grow MOF coatings of MIL-53(Al) and UiO-66(Zr) on the polymer surface, using the bottle itself as the synthesis reactor.
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In our novel green approach, the waste polyethylene terephthalate (PET) bottle material has effectively been used as the starting precursor instead of terephthalic acid for the synthesis of five terephthalate based nanoporous trivalent metal-organic frameworks (MOFs) namely MIL-47, MIL-53(Cr), MIL-53(Al), MIL-53(Ga), and MIL-101(Cr). The optimum reaction parameters to achieve the green synthesis were studied. These MOFs were structurally identified by using powder X-ray diffraction (PXRD) measurements. Scanning electron microscopy (SEM) images confirm the particle nature and size of the synthesized MOFs. Nitrogen gas sorption measurements have been done for some of the MOFs to check their porous properties. All the characterization techniques strongly supported that the synthesized MOFs using PET are similar to their literature reports. The gas adsorption studies for the synthesized MIL-53(Cr) and MIL-101(Cr) showed their significant gas uptake capability towards CO2 and H2 gases. Further, the synthesized MIL-47 and MIL-101(Cr) have been tested for their catalytic ability in chemical fixation of CO2 gas through the conversion of CO2 and epoxides to the corresponding cyclic carbonates which shows promising results to use them as catalysts.
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In this work, we synthesized Zr-fumarate MOFs by applying water as solvent and formic acid as modulator. Highly crystalline Zr-fumarate MOF obtained from 120 °C, 24 h synthesis conditions showed high thermal and hydro stabilities. Compared to the early reported MOF materials, the lower cost, more environmentally friendly synthesis process and comparable hydrogen uptake capacity make Zr-fumarate MOFs a good candidate for hydrogen storage applications. © 2015 Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Article
MIL-101(Cr), one of the most important prototypical MOFs, is well investigated and widely used in many scientific fields. With regard to MOF synthesis in general, the addition of a modifier is commonly used to improve the properties of the products. The effect of inorganic (mineral) and organic acid modifiers was thoroughly investigated in the synthesis of MIL-101(Cr) and HNO3 could increase the yield to over 80% of a product with average SBET > 3200 m2 g−1 in repeated experiments (from an average of 50% in most published syntheses) in small-scale laboratory synthesis. The large-scale synthesis could use the finding of HNO3 addition and produce MIL-101(Cr) in >100 g quantities with yields near 70% and BET-surface areas near 4000 m2 g−1. The addition of acetic acid (CH3COOH) together with seeding could decrease the reaction temperature, the lowest being 160 °C (from typically 220 °C in published procedures), with still relatively good yield and BET surface area of the product. The use of other strong inorganic or weak carboxylic acids as modulators typically caused a decrease in yield and porosity.
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MIL-101 promotes benzylic oxidation of hydrocarbons exclusively by molecular oxygen in the absence of any other oxidizing reagent or initiator. Using indane as model compound, the selectivity towards the wanted ol/one mixture is higher for MIL-101(Cr) (87 % selectivity at 30 % conversion) than for MIL-101(Fe) (71 % selectivity at 30 % conversion), a fact that was associated to the preferential adsorption of indane within the pore system. Product distribution and quenching experiments with TEMPO, benzoic acid and dimethylformamide show that the reaction mechanism is a radical chain autooxidation of the benzylic positions by molecular oxygen and the differences in selectivity have been attributed to the occurrence of the autooxidation mostly process inside or outside the MOF pores. MIL-101 is reusable, does not leach metals to the solution, and maintains the crystal structure during the reaction. Apparent accumulated TON values based on the metal content as high as 155,100 with TOF value of 19,350 h-1 were determined for this process that is carried out in the total absence of any oxidizing reagent besides oxygen. The scope of the benzylic oxidation was expanded to other benzylic compounds including ethylbenzene, n-butylbenzene, iso-butylbenzene, 1-bromo-4-butylbenzene, sec-butylbenzene and cumene.
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Poly(ethylene terephthalate) (PET) was chemically recycled through glycolysis with ethylene glycol (EG) and repolycondensation of its main depolymerized product bis(2-hydroxyethyl terephthalate) (BHET). In this process, synthesized sodium titanium tris(glycolate) was used as a new catalyst for both reactions. The catalytic efficiency and selectivity of sodium titanium tris(glycolate) in both reactions has been investigated and compared with conventional catalysts used in glycolysis or polycondensation. The results indicate that sodium titanium tris(glycolate) is a desirable catalyst for chemical recycling of PET because it can present high catalytic activity and selectivity not only in glycolysis but also in repolycondensation, which means high cost of the catalysts separation between two reactions during chemical recycling process could be avoided. Meanwhile, a mechanism of the glycolysis of PET catalyzed by sodium titanium tris(glycolate) was proposed based on the results of interactions among BHET, EG and catalysts revealed by infrared spectroscopy.
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“THE NUMBER WAS so unbelievably high, I thought it had to be a misprint.” That’s the way Ulrich Müller, a research director at BASF, recalls reacting in 1999 to the value given for the surface area of a novel microporous solid. As he perused a hot-off-the-press paper in Nature , Müller came across a study on metal-organic framework (MOF) compounds in which researchers reported measuring a surface area of some 3,000 m 2 /g ( 1999, 402 , 276). With a background in porous materials, Müller recognized that the reported surface area of the MOF compounds—crystalline materials composed of metal ions or clusters connected by way of organic linkers—surpassed that of many zeolites and activated carbon materials by an order of magnitude. Curious about the material, Müller contacted the study’s principal investigator, Omar M. Yaghi, now a chemistry professor at the University of California, Los Angeles, and requested a sample to analyze for himself. There was no misprint, Müller says. ...
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Metal-organic frameworks (MOFs) are constructed by linking inorganic units with organic linkers to make extended networks. Though more than 20 000 MOF structures have been reported most of these are ordered and largely composed of a limited number of different kinds building units, and very few have multiple different building units (heterogeneous). Although heterogeneity and multiplicity is a fundamental characteristic of biological systems, very few synthetic materials incorporate heterogeneity without losing crystalline order. Thus, the question arises: how do we introduce heterogeneity into MOFs without losing their ordered structure? This Review outlines strategies for varying the building units within both the backbone of the MOF and its pores to produce the heterogeneity that is sought after. The impact this heterogeneity imparts on the properties of a MOF is highlighted. We also provide an update on the MOF industry as part of this themed issue for the 150th anniversary of BASF. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Article
Hexagonal prism shaped monoliths of envelope density 0.40-0.467 g/cm3 and remarkable mechanical stability were obtained from MIL-101 powder. The hydrogen adsorption isotherms within an extended pressure range show that the excess adsorption decreases with the increasing density of the pellets. At 77 K and 150 bar, the total volumetric capacity is 46.5 g/L; the discharge to 159 K and 5 bar leads to 45 g/L (38.8 g/L referring to the outer tank volume) supporting MIL-101 as a promising candidate for applications in the 77-160 K range of interest for cryo-adsorption hydrogen storage method. The isosteric adsorption enthalpy evaluated from the experimental data with the van't Hoff equation, using fugacity, is in agreement with the calorimetric heat of adsorption reported in literature. Monoliths of this shape allow the best possible packing density of any sorbent in a container and the primary data reported here on MIL-101 could serve as material engineering properties required for modeling hydrogen storage tanks. Copyright (c) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Article
Modulated synthesis of MIL-101(Cr) in high yield and with good reproducibility using formic acid as a modulator is reported. Higher molar ratio of formic acid/CrCl3 was found to form better shape-defined MIL-101(Cr) crystals with higher surface area, larger pore volume and better hydrogen uptake performance. The highly crystalline MIL-101(Cr), composed of crystals in the size range of 100–150 nm with multifaceted surface, could be obtained in an optimized molar regime of CrCl3·6H2O/H2BDC/100HCOOH/550H2O at 210 °C for 8 h. The MIL-101(Cr) obtained from the modulated synthesis also showed high thermal and moisture stabilities as well as enhanced hydrogen storage capacity, making this material particularly promising for practical hydrogen storage applications.
Article
Hybrid materials of the metal–organic framework (MOF), chromium(III) terephthalate (MIL-101), and phosphotungstic acid (PTA) were synthesized in aqueous media in the absence of hydrofluoric acid. XRD analysis of the MIL101/PTA composites indicates the presence of ordered PTA assemblies residing in both the large cages and small pores of MIL-101, which suggests the formation of previously undocumented structures. The MIL101/PTA structure enables a PTA payload 1.5–2 times higher than previously achieved. The catalytic performance of the MIL101/PTA composites was assessed in the Baeyer condensation of benzaldehyde and 2-naphthol, in the three-component condensation of benzaldehyde, 2-naphthol, and acetamide, and in the epoxidation of caryophyllene by hydrogen peroxide. The catalytic efficiency was demonstrated by the high (over 80–90%) conversion of the reactants under microwave-assisted heating. In four consecutive reaction cycles, the catalyst recovery was in excess of 75%, whereas the product yields were maintained above 92%. The simplicity of preparation, exceptional stability, and reactivity of the novel composites indicate potential in utilization of these catalytic matrices in a multitude of catalytic reactions and engineering processes.
Article
A composite (Cr-G) made from chromium carbide (Cr3C2) and chemically converted graphene (G) was synthesized by calcining a Cr-based metal-organic framework (MIL-101) embedded with graphene oxide (GO). The MIL-101 embedded with graphene oxide (MGO) was synthesized by the self-assembly process of Cr(NO3)(3)center dot 9H(2)O and terephthalic acid in the presence of exfoliated GO in hydrothermal way. The incorporation of large amounts of GO did not prevent the formation of MIL-101 units. After calcination, the MGO decomposes to form a conductive composite consisting of sheet-like Cr3C2 and G sheets with CrN and Cr2O3 impurities confirmed by X-ray diffraction. The Cr-G modified glassy electrode (Cr-G/GCE) showed excellent response to the electro-oxidation of dopamine. Significantly, not like most other electro-catalysts, Cr-G/GCE maintained the linear growth meaning a single diffusion controlled process even at high scan rate of 300 mV s(-1). There was a low detection limit and broad linear range for Cr-G complex detection of dopamine.
Article
Well dispersed ultrafine Pd NPs have been immobilized in the framework of MIL-101, and tested for the catalytic hydrolysis of ammonia borane. The powder XRD, N2 adsorption-desorption, TEM, and ICP-AES were employed to characterize the Pd@MIL-101 catalyst. The as-synthesized Pd@MIL-101 exhibit the highest catalytic activity toward hydrolysis of AB among the Pd-based nano-catalysts ever reported, with the TOF value of 45 mol H2 min-1 (mol Pd)-1. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 64.
Article
A comparative adsorption study of three gases viz. CO, CO2 and CH4 on two adsorbents viz. Cu-BTC (or HKUST-1) and Cr-BDC (or MIL-101) is reported in this article. The gravimetric adsorption equilibrium measurements on the samples were performed in a Rubotherm magnetic suspension balance at three different temperatures: 295, 318 and 353 K and pressures ranging between 0 and 100 bar. Virial-Langmuir model was used to model the experimental data on Cu-BTC, whereas Dual Site Langmuir (DSL) model was used for adsorption on MIL-101. For all gases the enthalpy of adsorption at low loading was higher on MIL-101 than that on Cu-BTC, indicating the availability of open metal sites in case of MIL-101. Moreover, a sharp decrease in enthalpy of adsorption is observed in case of MIL-101, whereas only a moderate decrease is observed in case of Cu-BTC. CO has a large Henry’s constant on MIL-101, whereas at higher pressures, the solid exhibits better capacity for CO2. In case of Cu-BTC, CO2 has a higher capacity on the adsorbent as compared to the other two gases throughout the entire range of pressures studied. All the experimental data is critically analyzed by examining the role of open metal centers, adsorbate polarity and the effect of temperature on the electrostatic interactions.
Article
In this study, we have synthesized a hybrid composite of acid treated multi walled carbon nanotubes (MWCNTs) and metal organic framework MIL-101 and denoted as MWCNT@MIL-101. For synthesis of this composite, well dispersed MWCNTs in dimethylformamide were mixed with hydrofluoric acid solution of chromium nitrate nonahydrate and terephthalic acid. The MWCNT@MIL-101 obtained has the same crystal structure and morphology as that of virgin MIL-101, but carbon dioxide (CO2) adsorption capacity is increased about 60% (from 0.84 to 1.35 mmol g−1) at 298 K and 10 bar. The increment in the CO2 adsorption capacity of MWCNT@MIL-101 is attributed to the increase of micropore volume of MIL-101 by MWCNT incorporation.
Article
Scraps of waste PET bottle were successfully employed in two reactions as potent organic reagents to produce a lanthanide-free phosphor with intrinsic white and yellow photoluminescence property, providing a brand new perspective to chemical recovery of waste PET. Microwave synthesis was also explored to produce isotypic structures from which unforeseen variations in organic linker orientation were detected.
Article
The oligomeric fraction of polyethylene terephthalate (PET) has been studied as it has the potential to migrate to foods and beverages packaged in virgin and recovered PET plastics. We have applied positive ion atmospheric-pressure chemical ionisation (APCI) to extracts of food-grade PET resin and beverage bottles. A reversed-phase HPLC system was connected directly to a VG Platform mass spectrometer. An acetonitrile-water-acetic acid gradient elution was performed. Low APCI probe temperatures (as appropriate for a polyethylene glycol calibrant) produced no significant ions from a PET cyclic trimer standard. A high probe temperature of 500–600°C gave a strong protonated molecular ion.Characteristic spectra of the cyclic oligomers from the trimer to the heptamer were obtained. A second homologous series of substances 44 mass units higher than each PET oligomers eluted prior to each PET oligomer. The mass spectra indicated these to be oligomers with one monoethylene glycol unit replaced by a diethylene glycol unit. To our knowledge this is the first time that cyclic oligomers above the tetramer have been confirmed by LC-MS. The technique was considerably more sensitive than published thermospray methods and gave food spectra with sub-microgram quantities injected. This work demonstrates the advantages of APCI over thermospray as an MS technique for substances of this type.
Article
Metal–Organic Frameworks (MOFs) have emerged as potential hydrogen storage media due to their high surface area, pore volume and adjustable pore sizes. The large void space generated by cages in MOFs is not completely utilized for hydrogen storage application owing to weak interactions between the walls of MOFs and H2 molecules. These unutilized volumes in MOFs can be effectively utilized by incorporation of other microporous materials such as single walled carbon nanotubes into the pores of MOFs which could effectively tune the pore size and pore volume of the material towards hydrogen sorption. Single walled carbon nanotubes (SWNT) incorporated MIL-101 composite MOF material (SWNT@MIL-101) was synthesized by adding purified single walled carbon nanotube (SWNT) in situ during the synthesis of MIL-101. The powder X-ray diffraction patterns of SWNT@MIL-101 showed the structure of MOF was not disturbed by SWNT incorporation. Hydrogen sorption capacities of MIL-101 was observed to increase from 6.37 to 9.18 wt% at 77 K up to 60 bar and from 0.23 to 0.64 wt% at 298 K up to 60 bar. The increment in the hydrogen uptake capacities of composite MOF materials was attributed to the decrease in the pore size and enhancement of micropore volume of MIL-101 by single walled carbon nanotube incorporation.Highlights► Preparation of hybrid MOF material by incorporation of purified SWNT in MIL-101. ► Utilization of unused space in high surface area MOFs by micropore volume enhancement. ► Enhancement of hydrogen sorption at 77 K and 298 K in MIL-101 by SWNT incorporation. ► DFT calculations of CO2 adsorption isotherms at 273 K in MOF material to confirm ultramicropore formation.
Article
In this work, isotherm and kinetics of CO2 adsorption on a chromium-based metal organic framework MIL-101 sample were studied. The MIL-101 crystal cubes were synthesized by the microwave irradiation method and then characterized. The isotherms and kinetic curves of CO2 adsorption on the MIL-101 sample were separately measured at 298, 308, 318, and 328 K within a pressure range of 0−30 bar by a gravimetric method. The mass-transfer constants and diffusion activation energy Ea of CO2 adsorption on the MIL-101 crystals were estimated separately. Results showed that the maximum uptake of CO2 on MIL-101 was 22.9 mmol/g at 298 K and 30 bar and that isotherms of CO2 adsorption were well-fitted with the Freundlich model. The isosteric adsorption heat of CO2 on MIL-101 was in the range of 4.0−28.6 kJ/mol. It depended upon the amount of CO2 uptake and decreased with the loading of CO2. The adsorption kinetics of CO2 on the MIL-101 crystals was described by the linear driving force (LDF) model. With the increase of the temperature, the mass-transfer constants of CO2 adsorption on MIL-101 increased. The diffusion coefficients of CO2 were in the range from 4.11 × 10−11 to 2.54 × 10−10 cm2/s. The coefficients increased with the temperature and decreased with the pressure. The diffusion activation energies Ea of CO2 on MIL-101 were in the range of 2.62−4.24 kJ/mol, which decreased with the pressure.
Article
The injected specimens of recycled poly(ethylene terephthalate) (R-PET) and its blends with engineering PET (E-PET) are studied with differential scanning calorimetry (DSC). Specimens are dissected into three segments of (1) outer skin, (2) middle, and (3) the core for the topographic study of their separate crystallinities, which are induced by different crystallization rates in the injection mode. DSC thermograms reveal the different crystallinity states among these three segments with decreasing crystallinity from core to middle to the skin segments and the times and contact of injection-molded specimens with the mold during the cooling cycle after the injection of the specimens. With the same procedures of injection molding, comparisons of crystallinity among various specimens of virgin blow molding grade PET (B-PET), E-PET, and R-PET are made. There are little differences in crystallinity among three segments of B- or E-PET specimens. In contrast, a higher degree of crystallinity in the core segment than either middle or skin segments is observed for the R-PET. This may contribute to the faster crystallization rate of the R-PET in the mold. Specimens of R-/E-PET blends follow the R-PET pattern, even in 20% of R-PET in the blend. This faster crystallization rate of R-PET is confirmed with the lowering crystallization temperatures (Tc) of the R-PET and R-/E-PET blended specimens in the DSC heating process. Dynamic DSC cooling analysis reveals a high order of crystallinity in R-PET and R-/E-PET blends. Gel permeation chromatography (GPC) measurements of molecular weights and distributions support the orderly structure for R-PET. Terminal group analysis and intrinsic viscosity measurements of the R-PET support the chain modification of R-PET during the thermal treatments in accordance with the evidences of smaller Mw and narrower molecular-weight distribution from the GPC findings for the recycled PET. © 1996 John Wiley & Sons, Inc.
Article
In the present work, two metal–organic frameworks (MOFs), chromium benzenedicarboxylates MIL-53 and MIL-101, have been synthesized. A wide range of reaction conditions were explored in order to understand the effects of water concentration and acidity. It was found that MIL-101 is preferentially obtained when the water content is high and the acidity is low. On the contrary, concentrated reactants and high acidity lead to the formation of MIL-53. The steady conversion of MIL-101 into MIL-53 during the reaction, due to the difference in relative stability, was also confirmed. The effect of water may therefore be explained by the increase in reaction rate with increasing concentration of reactants. The MIL-53 is selectively obtained at low water content, because the MIL-101, a transient phase, even if formed initially, may be converted into MIL-53 because of the high reaction rate. Relatively low acidity (a pH of about 3) is beneficial to the synthesis of MIL-101 even though increased MIL-53 yield was expected at low acidity due to the accelerated deprotonation of terephthalic acid. The selective formation of MIL-101 at low acidity is probably because the concentration of a chromium trimer (the chromium species that is essential for the MIL-101 structure) increases with increasing pH. The concentration of the Cr trimer is more important than the concentration of benzenedicarboxylate for the synthesis of MIL-101.
Article
Poly(ethylene terephthalate) has been irradiated with UV light of different wavelengths and in various atmospheres. The extent of degradation was monitored by measuring the tensile strength, molecular weight, carboxylic acid endgroups, and fluorescence emission of the polymer. The importance of wavelengths <315 nm in causing deterioration was demonstrated to be mainly due to strong surface absorption which results in surface crazing and ultimate fracture under stress. Irradiation in nitrogen and under vacuum were found to give similar results, but with oxygen present in the system several significant differences were observed. In nonoxidative irradiations, crosslinking and discoloration of the polymer occurred. Under oxidative conditions, chain scissions and fluorescent material build-up resulted, whereas no crosslinking and only slight discoloration was observed. The possibility of a photo-oxidation reaction has thus been suggested, involving hydroperoxide formation, to explain the discrepancy in results obtained for the two types of environments.
Article
The synthesis of nanoporous chromium terepthalate MIL-101, using microwave irradiation and its benzene sorption ability, were investigated. The as-synthesized MIL-101 solid was purified by the method of microwave irradiation to obtain high porosity. The solid obtained from the process was cooled, filtered, washed with water, and dried at 150°C in air. The structure and crystallinity of the synthesized samples were determined using XRD analysis. The vapor-phase absorption of benzene was carried out at 30°C using a specially designed volumetric absorption apparatus, employing a constant-temperature oven. The samples were dehydrated under high vacuum before absorption and benzene was purified by freeze-pump-thaw cycles. The absorption capacity was calculated by the ideal gas law after absorption for 15 minutes at a constant temperature.
Article
The unusual properties such as high surface area, good thermal stability, uniform structured nanoscale cavities and the availability of in-pore functionality and outer-surface modification make metal-organic frameworks (MOFs) attractive for diverse analytical applications. However, integration of MOFs with magnets for magnetic solid-phase extraction for analytical application has not been attempted so far. Here we show a facile magnetization of MOF MIL-101(Cr) for rapid magnetic solid-phase extraction of polycyclic aromatic hydrocarbons (PAHs) from environmental water samples. MIL-101 is attractive as a sorbent for solid-phase extraction of pollutants in aqueous solution due to its high surface area, large pores, accessible coordinative unsaturated sites, and excellent chemical and solvent stability. In situ magnetization of MIL-101 microcrystals as well as magnetic solid-phase extraction of PAHs was achieved simultaneously by simply mixing MIL-101 and silica-coated Fe(3)O(4) microparticles in a sample solution under sonication. Such MOF-based magnetic solid-phase extraction in combination with high-performance liquid chromatography gave the detection limits of 2.8-27.2 ng L(-1) and quantitation limits of 6.3-87.7 ng L(-1) for the PAHs. The relative standard deviations for intra- and inter-day analyses were in the range of 3.1-8.7% and 6.1-8.5%, respectively. The results showed that hydrophobic and π-π interactions between the PAHs and the framework terephthalic acid molecules, and the π-complexation between PAHs and the Lewis acid sites in the pores of MIL-101 play a significant role in the adsorption of PAHs.
Article
The diverse structures and pore topologies, accessible cages and tunnels, and high surface areas make metal-organic frameworks attractive as novel media in separation sciences. Here we report the slurry-packed MIL-101(Cr) column for high-performance liquid chromatographic separation of substituted aromatics. The MIL-101(Cr) packed column (5 cm long × 4.6 mm i.d.) offered high-resolution separation of ethylbenzene (EB) and xylene, dichlorobenzene and chlorotoluene isomers, and EB and styrene. The typical impurities of toluene and o-xylene in EB and styrene mixtures were also efficiently separated on the MIL-101(Cr) packed column. The column efficiencies for EB, m-dichlorobenzene, and m-chlorotoluene are 20000, 13000, and 10000 plates m(-1), respectively. The relative standard deviation for five replicate separations of the substituted aromatics was 0.2-0.7%, 0.9-2.9%, 0.5-2.1%, and 0.6-2.7% for the retention time, peak area, peak height, and half peak width, respectively. The MIL-101(Cr) offered high affinity for the ortho-isomer, allowing fast and selective separation of the ortho-isomer from the other isomers within 3 min using dichloromethane as the mobile phase. The effects of the mobile phase composition, injected sample mass, and temperature were investigated. The separation of xylene, dichlorobenzene, and chlorotoluene on MIL-101(Cr) was controlled by entropy change, while the separation of EB and styrene on MIL-101(Cr) was governed by enthalpy change.