Shunsuke Tanaka

Kansai University · Department of Chemical, Energy and Environmental Engineering

Photocatalytic generation of H2O2 from water and O2 under sunlight is a promising artificial photosynthesis reaction to generate renewable fuel. We previously found that resorcinol–formaldehyde resin powders prepared with a high-temperature hydrothermal method become semiconductors comprising π-conjugated/π-stacked benzenoid–quinoid donor–acceptor...

Sunlight-driven photocatalytic dinitrogen (N2) fixation with water at ambient conditions is of vital importance for a sustainable energy society. The efficiency of this reaction, however, is still low because of the difficulty in promoting both water oxidation and N2 reduction reactions. Herein, we report that a high-phosphorus-doped carbon nitride...

In the long history of zeolite research, further enhancement of their acid strength has looked difficult. In this study, we achieved the enhancement by incorporating Ge into the zeolite framework. We synthesised the zeolites by a dry gel conversion method and characterised them in terms of morphology, crystal structure, and composition. We determin...

Nowadays, the increase in plastic waste is causing serious environmental problems. Catalytic cracking has been considered a promising candidate to solve these problems. Catalytic cracking has emerged as an attractive process that can produce valuable products from plastic wastes. Solid acid catalysts such as zeolites decompose the plastic waste at...

Hydrogen peroxide (H2O2) has received growing interest as an energy carrier. For the development of a sustainable energy society using H2O2 as a hydrogen carrier, the photocatalytic H2O2 splitting into H2 and O2 is a desirable reaction for the generation of H2. This reaction, however, is difficult to promote because the photoexcited electrons reduc...

For wide use and cost reduction of proton exchange membrane fuel cells (PEMFCs), the development of transition-metal-doped porous carbon (TMPC) electrocatalysts for the oxygen reduction reaction (ORR) is urgently needed. Herein, we report a new strategy for designing CoNx-doped carbon materials with fine-tuned porosity via anion exchange and CO2 ac...

Hydrogen is widely considered an emissions-free alternative energy carrier for sustainable energy devices, such as fuel cells and nickel-metal hydride batteries. Recently, electrochemical hydrogen evolution reaction (HER) from water splitting has been attracted as an eco-friendly process for producing hydrogen. Herein, we report a Co/P-doped carbon...

UiO-66, composed of Zr6O4(OH)4 cluster and 1,4-benzene dicarboxylate, is a promising material for practical chemical processes because it is known as one of the most thermally and chemically stable Metal...

The best way to synthesize industrially useful zeolites is to avoid the use of costly organic structure-directing agent (OSDA) and the generation of synthetic wastewater. Recently, the steam-assisted conversion methods...

Hierarchical microporous/mesoporous carbons with high surface area were successfully synthesized using a versatile approach based on ZnO nanoparticles. The advantages of the process in this study are that the mesopore-forming template can be removed by carbonization of the ZnO@sucrose composite without any need for washing and/or activation treatme...

Proton-exchange-membrane fuel cells (PEMFCs) are of considerable interest as a sustainable, renewable, efficient, and eco-friendly electrochemical conversion systems of energy. Sluggish oxygen reduction reaction (ORR) as the cathodic reaction have mainly dragged down the PEMFCs in practical use. The most effective catalyst for ORR today is a Pt-bas...

The generation of hydrogen peroxide (H2O2) from water and dioxygen by sunlight-driven heterogeneous photocatalysis is a promising method for the artificial photosynthesis of a liquid solar fuel. We previously found that resorcinol-formaldehyde (RF) resin powders prepared by high-temperature hydrothermal synthesis act as highly active semiconductor...

Zeolite-templated carbons (ZTCs) composed of curved and single-layer graphene frameworks have uniform micropores (ca. 1.2 nm) and high surface areas (~4,000 m²/g). Owing to their outstanding properties originating from the porous structures, ZTCs have been used in many applications. In this work, we synthesized Co/N-doped ZTC (Co/N-ZTC) by complexi...

OSDA/solvent‐free synthesis of zeolites is suitable for practical commercialization due to low environmental damage and low cost. However, only a few types of zeolites have been successfully synthesized by this method. In this study, ANA, CAN, GIS, SOD, FAU and LTA type zeolites were synthesized by the OSDA/solvent‐free synthesis method by changing...

The photocatalytic generation of hydrogen peroxide from water and dioxygen (H2O + 1/2O2 → H2O2, ΔG° = +117 kJ mol–1) under sunlight is a promising strategy for the artificial photosynthesis of a liquid fuel. We had previously found that resorcinol–formaldehyde (RF) resin powders prepared by the base-catalysed high-temperature hydrothermal method ac...

The mixed matrix membranes (MMMs) consisting zeolitic‐imidazolate framework‐8 (ZIF‐8) nanoparticles in a polymer have been of considerable interest in separation applications. The fillers used are mostly synthesized using the solvothermal method. In this study, the ZIF‐8 nanoparticles were synthesized using a solvent‐less and salt‐free mechanochemi...

The photocatalytic generation of hydrogen peroxide from water and dioxygen (H 2 O + 1/2O 2 → H 2 O 2 , ΔG° = +117 kJ mol ⁻¹ ) under sunlight is a promising strategy for the artificial photosynthesis of a liquid fuel. We had previously found that resorcinol-formaldehyde (RF) resin powders prepared by the base-catalysed high-temperature hydrothermal...

Fe/N doped porous carbons are promising non-precious electrocatalysts for oxygen reduction reaction (ORR). However, it is still hard to synthesize Fe/N doped porous carbons for ORR. Herein, we present a facile solvent-free method to synthesize Fe/N doped porous carbon as an ideal catalyst for ORR using resorcinol resin, Triblock copolymer Pluronic...

Recently, NiSx based catalysts are promising electrocatalysts for Hydrogen Evolution Reaction (HER) via water electrolysis. In particular, the S/Ni ratio is crucial to improve catalytic activity of NiSx based catalysts. Herein, we synthesized NiSx based catalysts (Ni/S/C) with a tuned S/Ni molar ratio using Ni²⁺ ions exchange resin. We succeeded in...

In this study, we have developed a new method to synthesize mesoporous titanium silicalite-1 (TS-1) with a higher content of active titanium in the framework (more than 5%) than that obtained from the conventional hydrothermal synthesis. The new method combines two methods as follows: (1) a sol-gel method in tetrahydrofuran for the synthesis of TiO...

An efficient and simple method was proposed to synthesize hierarchical and phosphorous-modified HZSM-5 zeolites by sequential alkaline and acid treatment. In the first NaOH alkaline treatment, intracrystalline mesoporosity was introduced into the zeolites by the crystal defect formation and growth of crystal defects due to desilication. The excessi...

Ammonia is an indispensable chemical. Photocatalytic NH3 production via dinitrogen fixation using water by sunlight illumination under ambient conditions is a promising strategy, although previously reported catalysts show insufficient activity. Herein, we showed that ultraviolet light irradiation of a semiconductor, bismuth oxychloride with surfac...

The sharp increase in current energy consumption needs the development of fuel cells (FCs) as one of sustainable, renewable, efficient and eco‐friendly electrochemical conversion systems of energy. The performance of electrocatalysts is crucially important for commercialization of FCs. Commercial Pt based catalysts are used due to their high cataly...

Photocatalytic N2 reduction with water by sunlight irradiation is a challenging issue towards sustainable energy society, but previously reported photocatalysts had suffered from low stability and low activity. We prepared a boron-doped carbon nitride (BCN) semiconductor powder loaded with nickel phosphide particles (Ni2P) as co-catalysts. The Ni2P...

Metal-organic frameworks (MOFs) possess a wide variety of potential applications in chemistry, biomedical engineering, and pharmaceutical fields. Systematic combinations of metal and organic components enable an unprecedented rational design of framework structures for each application. Of great importance to translating MOFs into practical technol...

Metal–Oorganic Framework (MOF) represents the largest class of materials among the crystalline porous materials ever developed. Their extremely uniform pore aperture and nearly unlimited structural and chemical characteristics have attracted great interest and promise in applying MOF to adsorptive and membrane–based separations. This review present...

ZIF-8 is a flexible zeolitic imidazole-based metal–organic framework and has been extensively studied because of its high structural stability. However, ZIF-8 is hydrolyzed in water at higher temperature, resulting in degradation of its crystalline and porous structure. In order to prevent ZIF-8 from structural collapse due to the hydrolysis reacti...

Artificial photosynthesis is a critical challenge in moving towards a sustainable energy future. Photocatalytic generation of hydrogen peroxide from water and dioxygen (H2O + 12\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgr...

Propane dehydrogenation (PDH) is one of the most promisng candidates of propylene production process to meet the growing demand of propylene in the future. There is an urgent need to develop catalysts for PDH. In this work, we have synthesized high silica Ga-Beta as a new candidate of the catalyst from dealuminated zeolite using dry gel conversion...

Zeolites have been applied in various chemical processes due to their multi-functionality. In practical use of zeolites, their hydrothermal stability is one of the important factors. We focused on the coating with hydrophobic silicalite-1, which is all silica MFI zeolite. In this work, we investigated the hydrothermal stability of ZSM-5 (MFI type a...

Au nanoparticles loaded on semiconductor TiO2 absorb visible light due to their surface plasmon resonance (SPR), and inject the photogenerated hot electrons (ehot-) into the conduction band of TiO2. The separated charges promote oxidation and reduction reactions. The step that determines the rate of the plasmonic photocatalysis on the Au/TiO2 syste...

Synthesizing high activity metal/heteroatoms-codoped carbon (M/H-C) electrocatalysts for oxygen reduction reaction is critical for commercialization of fuel cells, but it is still challenging because it is difficult to make the highly dispersed (M/H-C) electrocatalysts. Herein, commercial ion exchange resin-Amberlyst 15 is used as a support, and Co...

Metal organic framework (MOF) has been recognized as a fascinating class of solid crystalline materials which can be built with metal ions (or clusters) and organic linkers. Owing to their versatile chemical and engineering design, the more attention for MOF is shifting from its fundamental studies to industrial application including membrane separ...

Development of electrocatalysts for oxygen reduction reaction (ORR) is important to solve the current problems about energy and fuel. As one of the catalysts with high performance, platina group metals (PGM) based catalysts have been widely known. However, PGM based catalysts are not suitable for large commercial application since the PGM based cat...

An efficient and simple methodology was proposed to synthesize bimetallic Co–Zn based zeolitic imidazolate frameworks (CoZn-ZIFs; CoxZn(1−x)(2-methylimidazole)2) with sodalite topology. The synthesis strategy is based on a solventless mechanochemical reaction using only powder raw material, zinc oxide, cobalt acetate, and 2-methylimidazole, for eas...

An efficient and simple methodology was proposed to synthesize CHA zeolite without the use of solvent and OSDA. The synthesis strategy is based on a mechanochemical-assisted interzeolite transformation using only Na-type FAU zeolite and KOH as starting materials, for ease of handling and large-scale production. The role of KOH on crystal transforma...

Ammonia (NH3), which is an indispensable chemical, is produced by the Haber-Bosch process using H2 and N2 under severe reaction conditions. Although photocatalytic N2 fixation with water under ambient conditions is ideal, all previously reported catalysts show low efficiency. Here, we report that a metal-free organic semiconductor could provide a n...

In this work, a dual-functional catalyst with (1) catalytic activity of metal catalysts and (2) shape-selectivity of zeolites has been developed. We have fabricated Pt nanoparticles encapsulated in core-shell single crystal like silicalite-1 zeolite (CS-Pt/s-1) by a crystalline overgrowth method. The CS-Pt/s-1 catalyst showed much higher catalytic...

Zeolites have been conventionally synthesized using organic structure directing agents (OSDA) in solvent. In this work, we synthesized various zeolites from unseeded aluminosilicate via mechanochemical and vapor treatments in the absence of OSDA and solvent. Various types of zeolites were successfully synthesized from starting materials with differ...

ZIF-8 metal organic framework "micron-thick" films were constructed from ZnO precursor by a vapor-phase synthesis. The ZnO-to-ZIF-8 crystal transformation proceeded in the presence of 2-methylimidazole (Hmim) vapor. Continuous coatings of intergrown ZIF-8 crystals require control of a nucleation density. The dependence of ZnO crystal plane on the Z...

Photocatalytic production of hydrogen peroxide (H2O2) from earth-abundant water and O2 is one desirable artificial photosynthesis for solar fuel production. We prepared a metal-free hybrid photocatalyst consisting of pyromellitic diimide-doped carbon nitride (g-C3N4/PDI), boron nitride (BN), and reduced graphene oxide (rGO). The g-C3N4/PDI-BN-rGO c...

Metal organic framework (MOF) has been recognized as a unique molecular sieving material with flexible framework, enabling interesting “gate-opening” functionality. Recently, it is recognized that such structural transition is induced by molecular adsorption and controlling the crystal size and shape is an effective factor for regulating the struct...

An efficient and simple mechanosynthesis was proposed to synthesize zeolitic imidazolate-based metal organic framework ZIF-8 with hierarchical superstructure. The synthesis strategy is based on a concept that only uses precursor powders for ease of handling in the solid–solid mechanochemical reaction. The solvent-free conversion of ZnO to ZIF-8 cou...

Zeolitic imidazolate framework-8 shares the same topology with sodalite zeolite but consists of Zn nodes bridged by imidazolate linkers to form a neutral open-framework structure. ZIF-8 has been recognized as a unique molecular sieving material with a flexible framework enabling interesting “gate-opening” functionality. Controlling the crystal size...

Polycrystalline ZIF-8 membranes of about 1 µm in thickness were successfully grown on α-alumina porous support by seeding-free aqueous synthesis. In order to achieve continuous well-intergrown membranes, a pseudo-surface of ZIF-8 was formed on the support by chemical modification. Our membrane preparation in aqueous system is based on the support-s...

Various synthesis methods of zeolites have been established. Hydrothermal synthesis method with organic structure directing agent (OSDA) has been widely applied in zeolite synthesis. However, this method has some big problems in terms of industrial and environmental aspects: OSDA is expensive and thermally decomposed OSDA produces air pollution; an...

Zeolite have been widely applied as sophisticated solid acid catalysis in chemical industries. Tuning the acidic property of zeolites is very important to improve their catalytic performances and expand their utilization. Herein, we synthesized AEI type Ge incorporated aluminophosphate, GeAPO-18 by a dry gel conversion method in order to generate n...

Dehalogenation of aromatic halides is one important reaction for detoxification and organic synthesis. Photocatalytic dehalogenation with alcohol, a safe hydrogen source, is one promising method; however, early-reported systems need UV irradiation. We found that Pt-Pd bimetallic alloy nanoparticles (ca. 4 nm) supported on Ta2O5 (PtPd/Ta2O5), when a...

Generating hydrogen peroxide (H2O2) from water and dioxygen (O2) by photocatalysis is one ideal artificial photosynthesis for solar fuel production. Several early-reported powdered photocatalysts, however, produce small amounts of H2O2 (<0.1 mM). We prepared graphitic carbon nitride (g-C3N4) doped with mellitic triimide (MTI) units by thermal conde...

Visible light absorption of plasmonic Au nanoparticles supported on semiconductor TiO2 leads to injection of their photoactivated “hot electrons (ehot-)” into the TiO2 conduction band. This charge separation facilitates several oxidation and reduction reactions. These plasmonic systems, however, suffer from low quantum yields because the Schottky b...

A facile solvothermal method is developed to synthesize N-doped 3D bicontinuous macro/mesoporous carbon through co-gelation of in-situ polymerized N-enriched resin together with in-situ formed colloidal silica packing domains. The resultant material possesses abundant pyridinic/graphitic N, respectable surface area, and smooth pore channels (interc...

Partial oxidation of cyclohexane (CHA) to cyclohexanone (CHA-one) with molecular oxygen (O2) is one of the most important reactions. Photocatalytic oxidation has been studied extensively with TiO2-based catalysts. Their CHA-one selectivities are, however, insufficient because the formed CHA-one is subsequently decomposed by photocatalysis involving...

ZIF–8 is a flexible zeolitic imidazole-based metal organic framework (MOF) whose narrow pore apertures swing open by reorientation of imidazolate linkers and expand when probed with guest molecules. An interesting feature of the ZIF–8 MOF is that its crystal size can be varied over a wide range of values (typically from approximately 50 nm to 100 µ...

We successfully designed Zn ion doped ZSM-5/silicalite-1 core-shell zeolite catalyst. On methanol to para-xylene (MTpX) over the core-shell catalyst, p-xylene yield was 40.7 C-mol% and para-selectivity (para-xylene selectivity in xylene isomers) was higher than 99 C-mol%, which substantially exceeds the other results reported in the literature.

Photocatalytic hydrogen peroxide (H2O2) production from water and molecular oxygen (O2) by sunlight is a promising strategy for green, safe, and sustainable H2O2 synthesis. We prepared graphitic carbon nitride (g-C3N4) doped with electron-deficient biphenyl diimide (BDI) units by a simple calcination procedure. The g-C3N4/BDI catalyst, when photoir...

Pure lithium titanate (Li4Ti5O12) nanoparticles were synthesized at low temperature via a new simple method. First, amorphous titanium dioxide (TiO2) nanoparticles with a high surface area (624 m² g⁻¹) were prepared by using tetrahydrofuran (THF) as a solvent in the hydrolysis reaction of titanium tetraisopropoxide (TTIP) at room temperature. Pure...

Solar-to-chemical energy conversion is a challenging subject for renewable energy storage. In the past 40 years, overall water splitting into H2 and O2 by semiconductor photocatalysis has been studied extensively; however, they need noble metals and extreme care to avoid explosion of the mixed gases. Here we report that generating hydrogen peroxide...

ZIF-8 is a flexible zeolitic imidazole-based metal-organic framework whose narrow pore apertures swing open by reorientation of imidazolate linkers and expand when probed with guest molecules. This work reports on the crystal size dependency of both structural transitions induced by N2 and Ar adsorption and dynamic adsorption behavior of n-butanol...

Aerobic oxidation on a heterogeneous catalyst driven by visible light (λ >400 nm) at ambient temperature is a very important reaction for green organic synthesis. A metal particles/semiconductor system, driven by charge separation via an injection of "hot electrons (ehot-)" from photoactivated metal particles to semiconductor, is one of the promisi...

Photocatalytic production of hydrogen peroxide (H2O2) from ethanol (EtOH) and molecular oxygen (O2) was carried out by visible light irradiation (λ >420 nm) of mesoporous graphitic carbon nitride (GCN) catalysts with different surface areas, prepared by silica-templated thermal polymerization of cyanamide. On these catalysts, the photoformed positi...

Photoirradiation (λ>300 nm) of Degussa (Evonik) P25 TiO2, a mixture of anatase and rutile particles, in alcohols containing nitroaromatics at room temperature produces the corresponding imines with very high yields (80-96%). Other commercially-available anatase or rutile TiO2 particles, however, exhibit very low yields (<30%). The imine formation i...

Photoexcitation (λ>300 nm) of TiO2 loaded with Pt particles promotes selective hydrogenolysis of epoxides with alcohol as a reducing agent.

Zeolitic imidazolate frameworks (ZIFs) have received attention for membrane separation applications due to their zeolite-like permanent porosity and tunable uniformly-sized micropores. Although aqueous room temperature synthesis has apparently opened up environmental friendly and efficient ways to synthesize ZIFs, it poses challenges for membrane p...

Design of green, safe, and sustainable process for the synthesis of hydrogen peroxide (H2O2) is a very important subject. Early reported processes, however, require hydrogen (H2) and palladium-based catalysts. Herein we propose a photocatalytic process for H2O2 synthesis driven by metal-free catalysts with earth-abundant water and molecular oxygen...

Design of green, safe, and sustainable process for the synthesis of hydrogen peroxide (H2O2) is a very important subject. Early reported processes, however, require hydrogen (H2) and palladium-based catalysts. Herein we propose a photocatalytic process for H2O2 synthesis driven by metal-free catalysts with earth-abundant water and molecular oxygen...

Platinum (Pt) nanoparticles with <4 nm diameter loaded on graphitic carbon nitride (g-C3N4) by reduction at 673 K behave as efficient co-catalysts for photocatalytic hydrogen evolution under visible light (λ >420 nm). This is achieved by strong Pt-support interaction due to the high temperature treatment, which facilitates efficient transfer of pho...

Give it some stick: UV irradiation of spirothiopyran in an aqueous solution of gold nanoparticles (AuNPs) gives AuNP aggregates. The aggregate size is tuned by the photoirradiation time and the aggregation is facilitated by the covalent binding of photoisomerized spirothiopyran to the AuNPs surface. This binding decreases the electrostatic repulsio...

Mesoporous carbons were synthesized by organic–organic self-assembly of triblock copolymer F127 and phenolic resin oligomers composed of resorcinol–formaldehyde or resorcinol–furfural. The mesostructure control was performed by using different polymerization catalysts, ammonia and acetic acid. The effects of the aldehyde and polymerization catalyst...

The synthesis of zeolitic imidazolate framework-8 (ZIF-8) films in an aqueous system was achieved. ZIF-8 films with controllable thickness were successfully grown on a modified substrate at room temperature. The 3-(2-imidazolin-1-yl)propyltriethoxysilane (IPTES) was used to first form a pseudo-surface of ZIF-8 on a glass substrate, followed by laye...

Mechanochemical dry conversion that only uses zinc oxide and an imidazole ligand proved to be effective and reliable for fabrication of a zeolitic imidazolate framework with a polycrystalline grain boundary and a core-shell structure. The zinc oxide crystals are converted into a zeolitic imidazolate framework to a depth of approx. 10 nm below the s...

Rejuvenating sunlight: Supported Au-Cu bimetallic alloy nanoparticles promote aerobic oxidation at room temperature under visible light (λ>450 nm) irradiation with little deactivation by the oxidation of surface Cu atoms by oxygen. This is achieved through the reduction of oxidized surface Cu atoms by the surface Au atoms, a process which is activa...

Ordered mesoporous carbons have attracted great interest for their potential use to electrodes for electric double layer capacitors. However, it is crucial to develop an electrode such that the active sites within the mesoporous carbons are accessible to electrolyte solution species via facile mass transport through well-defined pores. Here, we inv...

We report here the synthesis of a zeolitic imidazolate framework-8 (ZIF-8) in an aqueous solution. ZIF-8 crystals were prepared by mixing 2-methylimidazole (Hmim) with Zn nitrate hexahydrate (Zn) in deionized water. The products prepared at high Hmim/Zn molar ratios were assigned to a sodalite (SOD)-type structure whose morphology consisted of a rh...

Highly ordered mesoporous silicoaluminophosphates were synthesized using LTA zeolite dissolved acidic solutions. In the first step, zeolite nanoblocks are prepared from zeolite crystals by dissolution of LTA in an H3PO4/HCl solution of carefully controlled concentration. In the second step, we combine the above solution and PEO106PPO70PEO106 triblo...

There is no universally accepted theoretical interpretation of the rate constant of the pseudo-second order kinetic model of adsorption. This study proposes a relationship for the rate constant of the pseudo-second order adsorption model based on the diffusion mass transfer of the adsorbate within spherical homogeneous adsorbent microspheres. This...

Monodisperse carbon spheres with coefficient of variation less than 4% were successfully synthesized through polycondensation of resorcinol with formaldehyde in the presence of ammonia as a catalyst followed by carbonization in an inert atmosphere. The diameters of the carbon spheres can be tuned in the range of 220–1140 nm by adjusting the ammonia...

We report that photoactivated rutile titanium dioxide (TiO2) catalyzes a highly efficient and selective hydrogenation of nitroaromatics with alcohol as a hydrogen source. Photoirradiation (λ >300 nm) of rutile TiO2 suspended in alcohol containing nitroaromatics at room temperature and atmospheric pressure produces the corresponding anilines with al...

We report here a simple and straightforward method that enables the size-controlled production of zeolitic imidazolate framework-8 in an aqueous system at room temperature. Pure single crystals with the size tuned in the range of ca. 300 nm to 3 gm in mean crystal size can be obtained and exhibit ultrahigh Langmuir surface area of above 1800 m(2) g...

Visible light irradiation (λ >450 nm) of platinum (Pt) nanoparticles supported on anatase titanium dioxide (TiO2) promotes efficient aerobic oxidation at room temperature. This occurs via the electronic excitation of Pt particles by visible light followed by the transfer of their electrons to anatase conduction band. The positively charged Pt parti...

Zeolite rho was prepared by hydrothermal synthesis using an 18-crown-6 ether (18C6) as a structure-directing agent, and the effects of the calcination temperature for removal of 18C6 on the physicochemical properties and CO(2)-adsorption properties were investigated. CO(2) adsorption on zeolite rho calcined at 150°C was lower than that on samples c...