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Environmental impact analysis of surface printing and 3D inkjet printing applications using an imine based covalent organic framework: A life cycle assessment study
... Apart from identifying the optimal material, the cost, poor technology readiness levels, and environmental impacts of production are some of the other major concerns raised in the survey. In this regard, developing greener synthesis routes, [173,174] and estimating cost, [175,176] and sustainability metrics [18,[177][178][179][180] of material synthesis are attainable targets. Through coordinated efforts between industry and academia, the transition of reticular materials from lab-to-market [7,181] may be promoted, yielding new industrial milestones and unlocking their full potential. ...
The field of reticular materials, such as metal–organic frameworks (MOFs) and covalent organic frameworks (COFs), is expanding continuously – be it in terms of novel structures, advanced characterization techniques, or record‐breaking physical properties for applications. This timeline review reflects on the progress over the past 30 years, complemented by input from the community of active researchers. Owing to a global, crowdsourced survey of 228 researchers that is conducted through an online questionnaire, recent insights into the demographics of the field are given. Besides revealing how it works, publish, and interact, the review highlights both academic and industrial milestones. The contemporary trends are described, both at the level of material development and their suitability for a range of applications. To pave the way for newcomers to the field, some remaining challenges and steps to overcome them are discussed. The findings from this contemplative review aim to shape the future course of research in this domain.
... The results showed that 3D printing has less impact on the environment. 307 The spatial structure of the COF is extremely stable, the COF exhibited good physical integrity and chemical stability, and it required little maintenance during use. 308 In addition, most COF materials currently available on the market can be recycled and the absorption rate of harmful substances can remain above 95% of the raw materials after repeated use. ...
Covalent organic frameworks (COFs) have gained considerable attention due to their design possibilities as the molecular organic building blocks that can stack in an atomically precise spatial arrangement. Since the inception of COFs in 2005, there has been a continuous expansion in the product range of COFs and their derivatives. This expansion has led to the evolution of three-dimensional structures and various synthetic routes, propelling the field towards large-scale preparation of COFs and their derivatives. This review will offer a holistic analysis and comparison of the spatial structure and synthesis techniques of COFs and their derivatives. The conventional methods of COF synthesis (i.e., ultrasonic chemical, microwave, and solvothermal) are discussed alongside the synthesis strategies of new COFs and their derivatives. Furthermore, the applications of COFs and their derived materials are demonstrated in air, water, and soil pollution management such as gas capture, catalytic conversion, adsorption, and pollutant removal. Finally, this review highlights the current challenges and prospects for large-scale preparation and application of new COFs and the derived materials. In line with the United Nations Sustainable Development Goals (SDGs) and the needs of digital-enabled technologies (AI and machine learning), this review will encompass the future technical trends for COFs in environmental pollution control. Key learning points (1) This review summarizes the research status of COFs and their derived materials in the field of environmental pollution control, which has never been summarized in detail. The application of COFs and derived materials in environmental pollution control was elaborated from three aspects of pollution. (2) It emphasizes the significance of AI and machine learning for COF research in the context of the rapid development of digitalization and IT. (3) Not only does it emphasize the strong research potential of COFs in the field of sustainable environment, but it also points out the future development direction of COFs, combining the UN SDG strategy and global policy development.
... -Errors in quantification: The multi-storey building contains 8.5 kg of copper per m 3 of the building volume. It seems unrealistic for this amount of copper to be found in buildings and it is possible the current data in ecoinvent may be overestimating the amount of copper in a building by more than a factor of 100 (Espada et al. 2023) as the consumption of non-renewable elements is pervasive in the analyses. ...
Purpose
A recent update to the Product Category Rules (PCRs) for Construction Products (of the International EPD System) has triggered a methodological issue for owners and users of Environmental Product Declarations (EPDs). The updated PCR has led to capital goods data being implicitly included in the Life Cycle Inventory (LCI) of EPDs. This paper critically examines the role of capital goods in EPDs and establishes major shortcomings in the current methodology, LCI datasets and interpretation.
Methods
To evaluate the role of capital goods in EPDs, this paper provides a discourse on the fundamentals of Life Cycle Assessment (LCA) methodology, scope, available LCI data and the impact of capital goods on EPD outcomes. Using the ecoinvent database, we analyse the impact of the inclusion and exclusion of capital goods in selected 38 construction products based on the EN 15804+A2 (2019) Standard. Finally, we estimate the relative contribution of capital goods to a suite of Life Cycle Impact Assessment (LCIA) indicators based on the archetypes of capital goods available in ecoinvent and apply Monte Carlo simulation to establish the range of uncertainties in the capital goods data for the selected construction products.
Results and discussion
Our research confirms that when capital goods are included based on currently available background LCI data, they mostly have a low effect (<10% increase) on climate change, but they can have an enormous effect (>100% increase) on abiotic depletion (minerals and metals), land use and/or human toxicity indicators. Interestingly, when looking further into the ecoinvent capital goods LCI datasets, it becomes clear that there are inaccuracies, inconsistencies, and possibly incorrect estimates of capital goods and infrastructure data. These findings raise questions about the suitability of the underlying LCI background data and whether non-attributable capital goods should be allowed to define EPD outcomes.
Conclusion
The requirement for the inclusion of capital goods leads to a major conundrum for LCA practitioners. It is suggested that capital goods be excluded until there is better refinement and improvement of the quality of LCI datasets and EPD programs provide clearer guidance on dealing with capital goods. Alternatively, EPDs could document transparently the inclusion or exclusion of capital goods, so that there is a clear separation of the effects of capital goods on LCIA indicators.
... The solvent choice for the processing into complex geometries through printing technologies also is a remarkable contributor, where 3D inkjet printing yields 5-65% lower impacts when compared to surface printing. [359] www.advancedsciencenews.com www.afm-journal.de ...
To help ensure a prosperous future on Earth for coming generations, academia and industry need to transform the way they plan and carry out the synthesis of novel materials to make them more environmentally sustainable. In particular, the field of reticular materials, i.e., metal‐organic frameworks, zeolitic imidazolate frameworks, and covalent organic frameworks, has great potential to outperform other materials and revolutionize various fields of applications. This review highlights several key aspects from the choice of their starting materials, solvents and synthetic methodologies that fall under the umbrella of the Green Chemistry principles, and incorporates a Circular Economy perspective by providing relevant strategies such as reuse, regeneration, or recycling to maximize the value of the Earth's available resources. Moreover, it will shed light on the life cycle assessment results of selected reticular materials and consider how constraints imposed by Green Chemistry principles, life cycle assessment metrics, and circular patterns will shape the future rational sustainable design and discovery of reticular materials.
... LCA analysis aims to calculate the environmental load based on an inventory analysis of the use of resources, energy, air, fuel, and others so that the environmental burden can be identified and then analyzed using different alternatives to reduce the impact. [16][17][18] The present study reported to identify and analyze input output based on inventory data from BSFL dried products and determine potential environmental impacts in the form of global warming potential (GWP), acidification (AC), terrestrial eutrophication (TE), fossil fuel depletion (FFE), and ecotoxicity (ET). ...
Background : Hermetia illucens L. have gained popularity in recent years as an environmentally friendly response to both the present and potential future food/feed crisis. The larvae of H. illucens L., or black soldier fly larvae (BSFL), is an alternative solution to tackle the issue of organic waste bioconversion. However, understanding the environmental loads associated with biowaste bioconversion using BSFL to produce dried BSFL is a pivotal point to keep the environment sustainable. This study reported a life cycle assessment (LCA) of the biowaste bioconversion process of BSFL and determined the environment impact analysis to make recommendations for modifications to lessen environmental consequences.
Methods : The methodology used is life cycle assessment (LCA), which includes: (a) system boundary determination (gate-to-gate), starting from biowaste production, biowaste bioconversion, prepupae and BSFL frass production. The system boundary of the dried BSFL production is designed for both the processing and production of one cycle of BSFL; (b) life cycle inventory activities carried out at PT Biomagg Sinergi Internasional, Depok, West Java, Indonesia; (c) conducting life cycle impact assessment on five environmental impact categories namely global warming potential (GWP), acidification (AC), terrestrial eutrophication (TE), fossil fuel depletion (FFE), eco-toxicity (ET); and (d) interpretation of the assessment result. The LCA is conducted using openLCA 1.11 software and TRACI 2.1 impact assessment method.
Results : The impact values of GWP, AC, TE, FFE, and ET, per 100 kg of BSFL dried production was 6.687 kg CO 2 eq; 0.029 kg SO 2 -eq; 0.092 kg N-eq; 16.732 MJ surplus; 121.231 CTUe. Production of prepupa had the highest hotspots in these emissions, followed dried BSFL production.
Conclusions: Efforts to reduce environmental impacts that can be done are by implementing an integrated rearing system using substrate from a single type of known substrate for BSFL and using alternative drying methods for BSFL dried production.
Environmental challenges that have led to climate change on Earth are among the most important issues facing contemporary humanity. Each industry, including the construction industry, plays a role in carbon dioxide production, a key factor in climate change. One of the innovative solutions for the construction industry to reduce environmental impacts is using plant-based biodegradable materials. There are significant opportunities for the use of biodegradable composites in 3D printing. This review article examined recent developments in biodegradable composites for 3D printing in architecture and explained the future perspective for researchers. It described the importance and characteristics of these materials, along with their types and applications. This review article mentioned recent innovations, their advantages for the environment and construction, and their capabilities. It listed the challenges of using these materials in architecture, the recycling and regulation methods related to them, and gave examples of materials used in architecture. This article compared biodegradable composites with traditional materials and discussed future directions in research.
An in-flight coalescence reactive inkjet printer has been developed to facilitate the in-air collision of two reactive microdroplets. This way precise volumes of reactive inks can be mixed and subsequently deposited on the substrate to produce the desired product by polymer synthesis and patterning in a single step. In this work, we validate the printer capabilities by fabrication of a series of 3D structures using an aliphatic polyurea system (isophorone diisocyanate IPDI and poly(propylene glycol) bis(2-aminopropyl ether) PEA-400). The influence of temperature and ink ratio on the material properties has been investigated. An increase in both IPDI and temperature facilitates the production of materials with higher Young's Modulus E and higher ultimate strength U. The possibility of printing different materials i.e. ductile (U = 2 MPa, ε B = 450%), quasi-brittle (U = 14 MPa, ε B = 350%), and brittle (U = 10 MPa, ε B = 11%) by varying the printing process parameters using one set of inks has been presented. The anisotropy of the material properties arising from different printing directions is at the 20% level.
Manufacturing sector is considered to be the second highest contributor in greenhouse gases emissions in EU, secondary to energy sector. The environmental impact of products, processes, and infrastructures of manufacturing is defined as the mass equivalent of carbon dioxide emissions, also known as carbon footprint, because carbon dioxide accounts for the largest portion of greenhouse gases emissions. The aim of this review is to show the impact of manufacturing on carbon emissions and to investigate the importance of carbon emission factors on the carbon footprint of manufacturing. This was performed via (1) mapping and categorizing the sources of carbon emission at process, machine, and system level; (2) identifying the weight factor of carbon emissions factors via sensitivity analysis; and (3) determining which carbon emission factor has the heaviest contribution in carbon footprint calculation. In all examples of the sensitivity analysis, it was shown that carbon emission factor for electrical energy was the only contributing factor at process level while being the strongest at machine level. At system level, the strongest contributor was the carbon emission factor for material production. To reduce the carbon emissions, one must identify the tuneable parameters at process, machine, and system level, from material, machine tool, and energy point of view. However, the highest reduction in carbon footprint can be achieved by reducing the carbon emission factors of electrical energy using renewable power sources such as solar or wind and by reducing the carbon emission factors for material production using recycling materials as “raw” material.
A life cycle assessment (LCA) was conducted on an innovative concrete 3D printing system, offering the following main advantages: (1) additive and subtractive capabilities, allowing for the automated post-processing of printed parts, including operations such as surface polishing, grooving and drilling and (2) the use of a cable robot, which is less expensive, lighter, more transportable, more energy-efficient and more easily reconfigurable than alternatives such as gantry-type systems. The production of a 4-m height structural pillar was assessed, comparing it to production with traditional methods, namely, using a mould. The study included the entire supply chain of the 3D printing equipment, operation and end-of-life, based on real data from the design and operation of a demonstration plant installed in Spain. Data for traditional construction was based on literature and expert judgement. The 3D production process included printing the pillar perimeter in four pieces with 3D printing concrete, transporting to the construction site and reinforcing and casting with conventional concrete. Traditional production involved reinforcing and casting with the mould on-site. The results show that when only one pillar needs to be produced, 3D printing has a lower environmental impact in all the environmental indicators assessed when compared to using a mould that is discarded after a single use. As an example, GHG emissions are lower by 38%. It was also found that the contribution of 3D printing to the environmental impact of producing a pillar is almost negligible, representing less than 1% of the pillar’s total GHG emissions. However, when the same pillar needs to be produced in higher numbers, the results show that 3D printing and conventional production have a similar environmental impact, given that the mould used in conventional production can be reused, becoming a comparatively efficient option.
Additive manufacturing (AM) is one of the fastest growing and most promising manufacturing technologies, offering significant advantages over conventional manufacturing processes. That is, the geometrical flexibility that leads to increased design freedom is not infinite as the numerous AM processes impose manufacturing limitations. Abiding by these manufacturability rules implies a backpropagation of AM knowledge to all design phases for a successful build. A catholic AM-driven design framework is needed to ensure full exploitation of the AM design capabilities. The current framework is based on the definition of the CAD aspects and the AM process parameters. Their dependence, affection to the resulted part, and weight on the total process determine the outcome. The AM-driven design framework prevents manufacturing issues of certain geometries, that can be effortlessly created by conventional manufacturing, and additionally exploits the full design-freedom potentials AM has to offer with a linear design flow reducing design iterations and ultimately achieving first time right AM design process.
Motivated by the rising costs of doing business overseas and the rise and implementation of digital technologies in production, new strategies are being explored to bring production and demand closer. While concepts like cloud computing, internet of things, and digital manufacturing increasingly gain relevance within the production activities of manufacturing companies, significant advances in three-dimensional (3D) printing technologies offer the possibility for companies to accelerate product development and to consider new supply chain models. Under this production scheme, material supply chains are redefined and energy consumption hotspots are relocated throughout the life cycle of a product. This implies a diversification of energy mixes and raw material sources that poses a risk of shifting problems between life cycle phases and areas of protection. This study compares a conventional mass scale centralized manufacturing system against a 3D printing-supported distributed manufacturing system on the basis of the production of one frame for eyeglasses using the life cycle assessment methodology. The study indicates clearly that the optimization potential is concentrated mainly in the energy consumption at the unit process level and exposes a close link to the printing material employed.
The direct interaction between CO2 and terminal alkynes in the presence of bis-(NHC)-metal catalysts at ambient conditions was studied. Two Cu and Ag-based bis-N-heterocyclic carbene Transition Metal catalysts were synthesized. The (NHC)2-Ag complex showed a better catalytic performance towards the carboxylation of terminal alkynes in comparison with the copper analogue even for the conversion of acetylene gas. The optimized conditions for the carboxylation are: the use of Cs2CO3 as additive, one atmosphere CO2 and room temperature using 1% mol catalyst. Mechanistic insight into the reaction mechanism is obtained by means of state-of-the-art first principles calculations.
Graphical Abstract
Trimerization of methyl-3-(dimethylamino) acrylate leading to 1,3,5-bezene tricarboxylate methyl ester and dimerization of 3-dimethylamino acrylonitrile leading to amino methylenated glutaconic acid dinitrile catalyzed by different acids in 1,2-dimethoxy ethane solvent is reported.
Sustainability, in terms of energy consumption and the emissions impact on both natural environment and human health constitute a major concern in modern society. In the current study, the environmental footprint of the processes related to the manufacturing of cylinder heads for a diesel and a petrol automotive powertrain is investigated with the use of Life Cycle Assessment (LCA) techniques. These two variants are investigated through different LCA techniques that share the same indicators, aiming at the method's objectivity. In addition, a comparison among different LCA methods has been conducted and the optimization challenges raised by their results have been discussed.
Three-dimensional covalent organic frameworks (3D COFs) were synthesized by targeting two nets based on triangular and tetrahedral
nodes: ctn and bor. The respective 3D COFs were synthesized as crystalline solids by condensation reactions of tetrahedral tetra(4-dihydroxyborylphenyl) methane or tetra(4-dihydroxyborylphenyl)silane and by co-condensation of triangular 2,3,6,7,10,11-hexahydroxytriphenylene. Because these materials
are entirely constructed from strong covalent bonds (C-C, C-O, C-B, and B-O), they have high thermal stabilities (400° to
500°C), and they also have high surface areas (3472 and 4210 square meters per gram for COF-102 and COF-103, respectively)
and extremely low densities (0.17 grams per cubic centimeter).
A facile, cost-effective, and green inkjet printing methodology is proposed for the fabrication of a transparent and conductive nanostructured indium tin oxide (ITO) thin films. Unlike solution deposition methods, the ITO nanoparticles did not deposit herein on the substrate. Instead, they are formed in-situ during the inkjet printing. The layer-by-layer inkjet printing is conducted stepwise, by printing the indium acetate based ink on a glass substrate, then printing the tin acetate-based inkjet ink onto a dry previously printed layer. Next, heat treatment is carried out leading to the formation of nanostructured ITO thin film. The resulting inkjet-printed sustainable transparent three-layer thin films were characteristic of evenly dispersed ITO nanodomains taking the advantage of appropriate wettability and rheological properties of the engineered ink solution. Surprisingly, the electrical resistivity of thin film drastically dropped (874 times) from 43.72 Ω cm for one-layer (48 nm thickness) to 0.05 Ω cm for three-layer (154 nm thickness) thin films, without sensible drop in optical properties (from 88% to 84% in the same order). In view of sustainability, i.e. low-cost clean inkjet printing, green chemicals used, and water-based synthesis, this novel technique opens new avenues for developing sustainable transparent thin films with superior electrical conductivity.
Perovskite solar cells (PSCs) have moved to the forefront of emerging thin-film solar cell research in just a decade, demonstrating the most promising efficiency records. These technological advancements however, were primarily tested at laboratory scale and there remains significant issues in relation to the scalability of the deposition methods utilised. Inkjet printing, initially used for printed electronics, has recently been applied to solar cell production and demonstrated promising potential for scaling up. Despite various studies that have assessed the technical feasibility of utilising inkjet printing, their environmental performance has not been investigated. This paper, for the first time, presents a comprehensive Life Cycle Assessment (LCA) study of inkjet printing-based PSCs, on a cradle-to-gate basis using GaBi LCA software. The results were compared with those of spin-coating, as the most widely studied deposition method, and demonstrated significant improvement in all impact categories. Global warming potential (GWP) and cumulative energy demand (CED) were used as proxies to compare results obtained in this paper with available studies in the literature. The comparison demonstrated that inkjet printing of PSCs had a GWP and CED of 7.54 kg CO2eq/m² and 200.18 MJ/m² while spin-coating had a reported median value of 74.5 kg CO2eq/m² and 1204 MJ/m² respectively. This suggests considerable environmental advantage for the inkjet method. The paper also assesses a novel green solvent-based precursor ink investigating the environmental benefits of eliminating the toxic and hazardous solvent materials commonly used in wet chemical deposition of perovskite layers. The green solvent-based precursor ink results demonstrated significant improvement over conventional solutions with up to six orders of magnitude lower impacts. The LCA results obtained in this paper contributes to forming a full assessment of the development of scalable deposition methods such as inkjet printing by highlighting their environmental hotspots and advantages. The paper also identifies potential opportunities for perovskite precursor ink material composition improvements for sustainable development of PSCs. This will assist in addressing their associated environmental concerns in relation to the use of high impact toxic solvents.
In this work, we have demonstrated the creation of monolithic covalent organic frameworks (COFs) through the use of in-air coalescence and reaction of inkjet printed monomer droplets. This method circumvents...
The world is moving towards a situation where resource scarcity leads to increased material cost, and the government is bound to dispose of heavy wastes generated by the growing population. Additive Manufacturing (AM) has bought a significant revolution in the current manufacturing processes. AM can fabricate complex and intricate shapes with ease. Material selection is an essential aspect in AM as a wide range of compatible materials available for AM. Appropriate material selection is necessary for cleaner production and sustainable development. Sustainable material selection considering various material properties and varied criteria can be effectively managed by Multi-Criteria Decision Making (MCDM) approach. However, several MCDM methods have a rank reversal problem, in which the rank of alternatives got changed when an alternative is added or removed from all considered alternatives. In this regard, this work presents a sustainable material selection of AM technologies. Sustainable material selection has been made for three AM technologies, namely Fused Deposition Modelling (FDM), Selective Laser Sintering (SLS), and Stereolithography (SLA). Four MCDM techniques have been used to analyze and compare AM materials, namely SAW (Simple Additive Weighting), MOORA (Multi-Objective Optimization based on Ratio Analysis), TOPSIS (Technique for order performance by similarity to ideal solution), and VIKOR (Vlsekriterijumska Optimizacija I Kompromisno Resenje). Rank reversal problems associated with MCDM methods are also highlighted in the material selection stage. The results reveal that 'TPU Elastomer', 'Accura HPC', and 'Duraform EX' are identified as the best material for FDM, SLA, and SLS based AM technologies. Further, practical and research implications have been derived based on the study to help industrial practitioners, researchers, and decision-makers for the selection of the best materials in the product development stage to support cleaner production.
Waste biomass for biofuels production can contribute to reduce dependence on fossil fuels and consequently, a decrease of CO2 emissions. In this work, the environmental feasibility of cardoon-to-bioethanol process was evaluated using Life Cycle Assessment (LCA). For this purpose, three processes involving different biomass pretreatments (dilute acid (DA), single steam explosion (SE) and steam explosion + alkaline extraction (SE + AE)) were simulated by using SuperPro Designer 9.5. Simulation results and literature data were used to perform LCA by using Gabi 6.0 software. LCA results showed that the pretreatment step is the main contributor to the overall impact in the dilute acid case due to the large energy requirements. The use of steam-explosion-based pretreatments drastically reduce environmental impacts regarding to DA process, being fertilizers, chemicals and enzyme production the main important contributors. By combining single steam explosion and subsequent alkaline extraction, the environmental performance is improved compared to single steam explosion due to a reduction of the energy consumption. However, higher toxicity impacts were obtained mainly because of the larger amount of enzyme and chemicals required. GHG emissions and energy balance of bioethanol from cardoon falls within the values reported for similar lignocellulosic raw materials. Finally, the comparative study of bioethanol from cardoon and fossil gasoline indicates that steam explosion-based processes are environmentally superior in most impact categories, obtaining a dramatic reduction of the primary energy demand (80%) and the GHG emissions (45%).
The introduction of new materials is tied to the rapid development of manufacturing processes. Additive manufacturing (AM) has been employed to fabricate a solid three-dimensional (3D) part directly from a computer-aided design (CAD) data. AM is an industrial process that has been widely employed in different industries in the past few years. In fact, this 3D printing is a rapid prototyping technology that involves a series of techniques. Although several challenges and limitations exist in the AM process currently, AM is expected to revolutionize the manufacturing process of engineering components. However, despite the numerous applications of AM techniques in various industries, their environmental impacts are not well documented. AM affords significant changes in production cost, energy consumption, and manufacturing lead times. All these issues have been considered to develop this technology to have higher efficiencies and lower environmental impacts. In this paper, we briefly review AM methods and discuss their environmental impacts. Furthermore, we present the main advantages and disadvantages of AM processes involving polymers. It can be concluded that AM is advantageous in some cases, exhibiting lower energy consumption and comprising shorter manufacturing processes. The analysis and discussion indicate the advantages, limitations, and future research directions for the industrial applications of AM.
Covalent organic frameworks (COFs) enable precise reticulation of organic building units into extended 2D and 3D open networks using strong covalent bonds to constitute predesignable topologies and tunable pore structures, presenting an emerging class of crystalline porous polymers. Although rapid progress and substantial achievements in COF chemistry over the past 15 years have been realised, highly efficient strategies and reproducible procedures still play a central role in achieving high-quality COFs and serve as a major driving force for the further advancement of this promising field. In this review, we focused on the key progress in synthesising high-quality COF crystallites and films by highlighting their uniqueness from the viewpoints of synthetic strategies and procedures. We discussed representative synthetic methods including mechanochemical synthesis, microwave synthesis, multicomponent reaction, multistep synthesis and linker exchange strategies to compare their features in producing COFs. We scrutinised the recently developed “two-in-one” molecular design strategy to showcase advantages in optimising synthetic conditions such as catalyst, monomer feeding rate and tolerance to functional groups. We analysed interfacial polymerisation for fabricating various COF films by emphasising their scope and applicability. Moreover, we proposed key underlying challenges to be solved and predicted future frontiers from the perspectives of synthesising high quality crystallites and films that are key to practical applications.
The induction of macro and mesopores into two-dimensional porous covalent organic frameworks (COFs) could enhance the exposure of the intrinsic micropores toward the pollutant environment, thereby, improving the performance. However, the challenge is to build a continuous hierarchically porous macro-architecture of crystalline organic materials in the bulk scale. In this regard, we have strategized a novel synthetic method to create hierarchically porous COF foams consisting of ordered micropores (2–2.2 nm), disordered meso and macropores (50 nm to 200 µm) as well as ordered macropores (1.5 mm to 2 cm). Herein, graphene oxide was used for creating disordered macro and meso pores in COF-GO foams. Consider-ing the rheological features of the precursor hydrogel, we could integrate crystalline and porous COF-GO foams into self-supported 3D-printed objects with the desired shapes and sizes. Therefore, we have engineered the 3D macro-architecture of COF-GO foams into complex geometries keeping their structural order and continuous porosity intact over a range of more than a million (10-9 m to 10-3 m). The interconnected 3D openings in these COF-GO foams further enhance the rapid and efficient uptake of organic and inorganic pollutants from water (>95% removal within 30 s). The abundant distribution of interconnected macroporous volume (55%) throughout the COF-GO foam matrix enhances the flow of water (1.13 × 10-3 m.s−1) which results in efficient mass transport and adsorption.
Covalent organic frameworks (COFs), as an emerging class of crystalline porous polymers connected by dynamic covalent bonds, have been well studied over the past decade. Recently, three dimensional (3D) COFs have attracted extensive interest for the synthesis and applications of novel COFs. The principal reason for this rising trend is based on their unique porous features and excellent performances compared to previously reported two dimensional (2D) frameworks with the layered AA-stacking mode. This critical review describes the current state-of-the-art development of 3D COFs in the design principles, synthetic methods, functionalization strategies, and potential applications. Some major challenges associated with future perspectives are further discussed, inspiring the development of 3D COFs.
Covalent organic frameworks (COFs) are a class of crystalline porous organic polymers with permanent porosity and highly ordered structures. Unlike other polymers, a significant feature of COFs is that they are structurally predesignable, synthetically controllable, and functionally manageable. In principle, the topological design diagram offers geometric guidance for the structural tiling of extended porous polygons, and the polycondensation reactions provide synthetic ways to construct the predesigned primary and high-order structures. Progress over the past decade in the chemistry of these two aspects undoubtedly established the base of the COF field. By virtue of the availability of organic units and the diversity of topologies and linkages, COFs have emerged as a new field of organic materials that offer a powerful molecular platform for complex structural design and tailor-made functional development. Here we target a comprehensive review of the COF field, provide a historic overview of the chemistry of the COF field, survey the advances in the topology design and synthetic reactions, illustrate the structural features and diversities, scrutinize the development and potential of various functions through elucidating structure-function correlations based on interactions with photons, electrons, holes, spins, ions, and molecules, discuss the key fundamental and challenging issues that need to be addressed, and predict the future directions from chemistry, physics, and materials perspectives.
Reactive inkjet printing holds great prospects as a multi-material fabrication process due to its unique advantages involving customization, miniaturization, and precise control of droplets for patterning. For inkjet printing of hydrogel structures, a hydrogel precursor (or cross-linker) is printed onto a cross-linker (or precursor) bath or a substrate. However, the progress of patterning and design of intricate hydrogel structures using the inkjet printing technique is limited by the erratic interplay between gelation and motion control. Accordingly, micro-reactive inkjet printing (MRIJP) was applied to demonstrate a spontaneous 3D printing of hydrogel microstructures by using alginate as the model system. In addition, a printable window within the capillary number-Weber number for MRIJP technique demonstrated the importance of velocity to realization of in-air binary droplets collision. Finally, a systematic analysis shows that the structure and diffusion coefficient of hydrogels are important factors that affect the shape of printed hydrogels over time. Based on such a fundamental understanding of MRIJP printing of hydrogels, the fabrication process and the structure of hydrogels can be controlled and adapt for 2D/3D microstructure printing of any low-viscosity (<40cP) reactive inks, with a representative tissue-mimicking structures of ~200 μm diameter hollow tube presented in this work.
Previously perceived as a rapid prototyping technique, additive manufacturing (AM) has evolved into a fully developed manufacturing process, with growing accessibility to different industrial sectors. Its technological and economic advantages are frequently documented, but AM's environmental performance is seldom investigated. Not long ago discrete initiatives to assess AM's applicability for building large-scale structures started to arise. Mostly focused on technical and economic feasibility, these studies pave the way for the process's consolidation in the construction sector. This paper aims to systematically and critically assess the available literature on AM's life cycle environmental impacts and to identify the main challenges and trends on loads measurements. The findings help feed recommendations to perform life cycle assessments (LCA) in AM initiatives, with a special focus on the construction sector. A systematic search led to the careful analysis of 52 papers, out of 353 that matched our search protocol. In terms of LCA methods' robustness, a lack of transparency stood out in many papers, suggesting that authors were most likely non-LCA experts, applying the tool without much knowledge of requirements and modelling intricacies. In terms of documented global warming potential (GWP) values in comparison to conventional manufacturing (CM), AM processes were portrayed as beneficial in most cases. Most papers documented results ranges, which represented different printing, production or distribution strategies, in which AM's performance varied considerably. LCA played a significant role in finding an optimum production approach and seems to be a valuable lens to assure 3D printing's environmental competitiveness. A contribution analysis showed that there is a shift between materials vs. production processes contribution in the life cycle GWP loads of systems manufactured with AM and CM. 3D printing processes account for almost 80% of AM's total GWP, while for CM that position is held by the material-related loads. For construction related AM processes, the material intensity is, however, still by far the largest contributor to building systems' GWP, maintaining the impact distribution as in typical manufacturing processes.
Covalent organic frameworks (COFs) are an emerging class of new organic polymers showing tuneable permanent porosity and crystallinity. They are formed, using modular chemistry concepts, by condensation reactions between their molecular precursors based on the formation of dynamic bonds. Despite much effort having been devoted towards the design of the physical and/or chemical properties of these materials by selecting their initial building blocks, the importance of processability for their applications has only recently emerged. This tutorial review article rationalizes the strategies used so far on COF processability leading to the formation of thin-films, membranes, or individual particles with controlled shape and size as well as composite fabrication. We aim to provide a rational perspective of the importance of COF processability towards potential applications of COFs in many different fields which are at the forefront of research in materials science.
This work presents a “cradle-to-gate” Life Cycle Assessment (LCA) of 3D-printing polymerisable ionic liquids (PILs) using digital light projection (DLP). It is based on primary data from environmental emissions, wastewater, chemical components, and manufacturing of PIL based devices. The results indicate that the printing process does not significantly exacerbate the environmental impacts. However, it is shown that excellent opportunities for further mitigation of the life cycle impacts of PILs can be realised are by practising reagent recovery, which reduces the amount of reagents emitted as waste, and by reduction/recycling of solvents used for cleaning the 3D part. The major impact contributor in the 3D-printing of PILs is the synthesis of the IL monomers. The effective reduction of solvent consumption and recovery significantly improves the impact of the synthetic process. This work focuses on the employment of the 3-butyl-1-vinylimidazolium [BVim] cation, with the non-coordinating and hydrophobic bis(trifluoromethane)sulfonimide [NTf2]- anion as the counter anion. The polymerisable monomer IL has comparable impact compared to the analogous non-polymerisable 3-butyl-1-methylimidazolium [NTf2]- ionic liquid, thus potentially allowing for the more efficient use of the ionic liquid properties by immobilization in solid phases. Furthermore, it is demonstrated that switching the anion from [NTf2]- to dicyanamide [N(CN2)]- significantly decreases the impacts in all categories evaluated for PIL production. This work represents the first phase toward quantitative LCA data generation for the process of 3D-printing ionic liquids, which will be great support for decision making during design of PIL 3D-printing processes at a laboratory scale.
As a newly emerging class of porous materials, covalent organic frameworks (COFs) have attracted much attention due to their intriguing structural merits (e.g., total organic backbone, tunable porosity and predictable structure). However, the insoluble and unprocessable features of bulk COF powder limit their applications. To overcome these limitations, considerable efforts have been devoted to exploring the fabrication of COF thin films with controllable architectures, which open the door for their novel applications. In this critical review, we aim to provide the recent advances in the fabrication of COF thin films not only supported on substrates but also as free-standing nanosheets via both bottom-up and top-down strategies. The bottom-up strategy involves solvothermal synthesis, interfacial polymerization, room temperature vapor-assisted conversion, and synthesis under continuous flow conditions; whereas, the top-down strategy involves solvent-assisted exfoliation, self-exfoliation, mechanical delamination, and chemical exfoliation. In addition, the applications of COF thin films including energy storage, semiconductor devices, membrane-separation, sensors, and drug delivery are summarized. Finally, to accelerate further research, a personal perspective covering their synthetic strategies, mechanisms and applications is presented.
Decomposition and repolymerization of conjugated polymers offer great promise for developing recyclable photothermal conversion materials, which yet remain challenging. Herein, a crosslinked conjugated polymer based on a dynamic covalent bond of Schiff base is developed. This polymer possesses photothermal conversion efficiency as high as 90.4%. Decomposition of the polymer under specialized conditions is corroborated by various characterizations. The kinetics study is also investigated to understand this degradation process. Furthermore, those decomposed species can be repolymerized back to conjugated polymers which possess the same photothermal conversion efficiency as the pristine polymer. Such a degradable and recyclable photothermal polymer is successfully used as a heat source for photothermal‐electrical conversion to generate Seebeck voltage under either near infrared (NIR) irradiation or solar illumination.
The chrome plating industry originates wastewater containing hazardous pollutants as hexavalent chromium. In this work, two alternatives for the treatment of the wastewater streams generated in a Spanish chrome-plating plant are studied from environmental and techno-economic perspectives. Both scenarios include the operations needed to obtain a chromate material and the further treatment of the produced wastewater. In the base scenario, the wastewater rich in Cr(VI) is treated through a sequential reduction - precipitation - settling process. In the alternative scenario the treatment of the wastewater consists of ionic exchange and photocatalytic process, which allows reducing Cr(VI) content by the use of solar light. Life Cycle Assessment (LCA) was applied to both scenarios in order to determine the most important impacts. For that purpose, data provided by a chrome-plating plant, experimental data obtained in the laboratory and results of process simulation were used to build up the inventory data. Obtained results show that the main impact in the base scenario is the disposal of the solid sludge, obtained as waste, due to intensive energy consumption. Regarding the alternative scenario, the use of chemicals is the main contributor to environmental impacts. By comparing both scenarios, the alternative one presents a clear improvement of the environmental performance, reducing about 85% the environmental damage. Finally, techno-economic evaluation results reveal that the cost of the alternative process per unit of treated water is about 15% higher than in the case of the conventional treatment.
A framework for molecular assembly
Covalent molecular frameworks are crystalline microporous materials assembled from organic molecules through strong covalent bonds in a process termed reticular synthesis. Diercks and Yaghi review developments in this area, noting the parallels between framework assembly and the covalent assembly of atoms into molecules, as described just over a century ago by Lewis. Emerging challenges include functionalization of existing frameworks and the creation of flexible materials through the design of woven structures.
Science , this issue p. eaal1585
Hydrazine sulfate product: hydrazine sulfate (NH 2 NH 2 · H 2 SO 4 )
We report herein an efficient, fast, and simple synthesis of an imine-based covalent organic framework (COF) at room temperature (hereafter, RT-COF-1). RT-COF-1 shows a layered hexagonal structure exhibiting channels, is robust, and is porous to N2 and CO2 . The room-temperature synthesis has enabled us to fabricate and position low-cost micro- and submicropatterns of RT-COF-1 on several surfaces, including solid SiO2 substrates and flexible acetate paper, by using lithographically controlled wetting and conventional ink-jet printing.
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Two-dimensional covalent organic frameworks (COFs) are polymer networks that organize molecular building blocks into porous, layered structures of interest for organic optoelectronic and energy storage devices. Current synthetic methods produce these materials as either insoluble, microcrystalline powders or as oriented thin films on various substrates, including single-layer graphene (SLG). Under these conditions, COF thin films form on both the graphene-coated and bare regions of the substrate, suggesting uncontrolled nucleation processes that occur either in solution or nonselectively on different surfaces. Here, we describe modified polymerization conditions that provide COF films selectively on SLG. This finding enables COF films to be grown on lithographically patterned SLG substrates, which provide insight into the uniformity of film growth across the substrate and factors relevant to their nucleation and growth. The ability to grow COF films selectively on lithographically patterned SLG will facilitate their integration into devices. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014
A mesoporous electron-donor covalent organic framework based on a benzodithiophene core, BDT-COF, was obtained through condensation of a benzodithiophene-containing diboronic acid and hexahydroxytriphenylene (HHTP). BDT-COF is a highly porous, crystalline and thermally stable material, which can be handled in air. Highly porous, crystalline oriented thin BDT-COF films were synthesized from solution on different polycrystalline surfaces, indicating the generality of the synthetic strategy. The favorable orientation, crystallinity, porosity and the growth mode of the thin BDT-COF films were studied by means of X-ray diffraction (XRD), 2D grazing incidence diffraction (GID), transmission and scanning electron microscopy (TEM, SEM) and krypton sorption. The highly porous thin BDT-COF films were infiltrated with soluble fullerene derivatives, such as [6,6]-phenyl C61 butyric acid methyl ester (PCBM), to obtain an interpenetrated electron-donor/acceptor host-guest system. Light-induced charge transfer from the BDT-framework to PCBM acceptor molecules was indicated by efficient photoluminescence quenching. Moreover, we monitored the dynamics of photo-generated hole-polarons via transient absorption spectroscopy. This work represents a combined study of the structural and optical properties of highly oriented mesoporous thin COF films serving as host for the generation of periodic interpenetrated electron-donor and electron-acceptor systems.
Chromtrioxid (I) reagiert mit Pyridin und 6 n HCl zum Pyridiniumchlorchromat (II), das ein leicht zu handhabendes Oxidationsmittel für die Umwandlung von Alkoholen zu Aldehyden und Ketonen darstellt.
For gas phase synthesis of pyridine bases from acetaldehyde, formaldehyde, and ammonia (known as the Chichibabin reaction), we have developed an efficient catalyst based on the pentasil zeolite (ZSM-5) treated with a metal cation such as Pb, Tl, or Co. Compared with a conventional amorphous silica-alumina catalyst, this catalyst affords not only a much higher yield of total pyridine bases, but also a higher yield of more valuable pyridine. The comparison between synthesis reactions of pyridine, 2,6-lutidine and 2,4,6-collidine has clarified that the high pyridine selectivity comes from the shape-selectivity of the pentasil zeolite, and that the density of the active sites in an inner channel of zeolite is much higher than those on the outer surface.The activity of the zeolite catalyst decreased gradually with repeated reaction-regeneration cycles. We have solved this problem by developing a new regeneration method. This method consists of two elements: (1) an addition of a trace amount of a noble metal (Pt) to the zeolite as a co-catalyst for aeration; and (2) an addition of a small amount of alcohol in the aeration gas. As a result, the catalyst life has been extremely improved.
We report on the synthesis and self-assembly of a new series of discotic molecules containing triphenylbenzene as the core and alkoxy side chain with varying length. It was found that compounds 3 a-c, 4 b and 5 b could form stable gels in several apolar solvents. Transmission electron microscopy (TEM) images revealed that their morphologies were very different for the different alkoxy-substituted organogels. In toluene or hexane, 3 b and 3 c resulted in both left- and right-handed helical fibers, whereas 3 a resulted in straight rigid fibers; 4 b and 5 b resulted in most straight fibers with a few twisted fibers. The results from FT-IR and UV/Vis absorption spectroscopy indicated that the hydrogen bonding and pi-pi interactions were the main driving forces for the formation of the self-assembled gels. Further detailed analysis of their aggregation modes were conducted by UV-visible absorption spectra and X-ray diffraction (XRD) measurements. Based on these findings, the influence of these peripheral alkoxy substituents on the gel formation and the aggregation mode were discussed. The special enhanced fluorescent emissions, which resulted from aggregation, were also found in the gel phase.
Covalent organic frameworks (COFs), in which molecular building blocks form robust microporous networks, are usually synthesized as insoluble and unprocessable powders. We have grown two-dimensional (2D) COF films on single-layer graphene (SLG) under operationally simple solvothermal conditions. The layered films stack normal to the SLG surface and show improved crystallinity compared with COF powders. We used SLG surfaces supported on copper, silicon carbide, and transparent fused silica (SiO(2)) substrates, enabling optical spectroscopy of COFs in transmission mode. Three chemically distinct COF films grown on SLG exhibit similar vertical alignment and long-range order, and two of these are of interest for organic electronic devices for which thin-film formation is a prerequisite for characterizing their optoelectronic properties.
An unusual oxidative cyclization of a N-hydroxy pyridone 9 with Z-2-cyclodecenone 11 has been achieved, thus demonstrating a possible biomimetic route to pyridomacrolidin 2. [reaction: see text]
Covalent organic frameworks (COFs) have been designed and successfully synthesized by condensation reactions of phenyl diboronic
acid {C6H4[B(OH)2]2} and hexahydroxytriphenylene [C18H6(OH)6]. Powder x-ray diffraction studies of the highly crystalline products (C3H2BO)6·(C9H12)1 (COF-1) and C9H4BO2 (COF-5) revealed expanded porous graphitic layers that are either staggered (COF-1, P63/mmc) or eclipsed (COF-5, P6/mmm). Their crystal structures are entirely held by strong bonds between B, C, and O atoms to form rigid porous architectures
with pore sizes ranging from 7 to 27 angstroms. COF-1 and COF-5 exhibit high thermal stability (to temperatures up to 500°
to 600°C), permanent porosity, and high surface areas (711 and 1590 square meters per gram, respectively).
- Braun
Glyrecol α,γ-dichlorohydrin
- Conant