Encapsulation of multiple enzymes in a metal–organic framework with enhanced electro-enzymatic reduction of CO2 to methanol

MOF-based materials for photo- and electrocatalytic CO2 reduction

Emerging Nanomaterials for Light‐Driven Reactions: Past, Present, and Future

Local Weak Hydrogen Bonds Significantly Enhance CO ₂ Electroreduction Performances of a Metal–Organic Framework

Anode-Driven Controlled Release of Cathodic Fuel via pH Response for Smart Enzymatic Biofuel Cell.

Advances in Emerging Crystalline Porous Materials.

Hierarchical Pore Structures as Highways for Enzymes and Substrates

Achieving efficient CO2 electroreduction for production of valuable chemicals requires affordable, stable, and non-toxic catalysts. One of the most studied and promising products of CO2 reduction is formic acid/formate. The latter species is receiving increased attention as an energy vector [1] or energy storage media (e.g., in CO2 redox flow batteries [2]). At present, the practical application of CO2 reduction to formate still faces challenges due to the lack of electrocatalysts capable of operating at high current densities (> 200 mA cm−2) with low degradation over long-duration operation [3].Traditional metallic catalysts like Bi, Sn, In or Pb when scaled in flow cells typically suffer from low faradaic efficiencies (< 70%) at current densities ≥ 200 mA cm-2, coupled with inadequate durability [4]. Metal-organic frameworks (MOFs) present promising and thus far largely unexplored attributes as electrocatalysts for CO2 reduction, including high atom utilization during catalysis due to their porous crystal structure and tunable pore size distribution [5,6]. However, they also face challenges related to high overpotentials and complex synthesis methods [7].This study elucidates the efficacy of a Bi metal-organic framework (Bi-MOF) synthesized through a rapid and facile method. The Bi-MOF obtained by our proprietary novel method [8], exhibits exceptional catalytic performance. Notably, it demonstrates outstanding faradaic efficiencies towards formate (FEHCOO - = 95–100%) at current densities up to 1 A cm−2 in a gas diffusion electrode, at low catalyst loading (0.5 mg cm−2).Moreover, Bi-MOF displays extended stability, operating continuously for over 20 hours at an industrially relevant current density (200 mA cm−2) and without electrolyte (1.5 M KOH) replenishment. In a flow reactor with 10 cm2 electrode geometric area, a 100% FEHCOO - was obtained during 2-hour electrolysis at 100 mA cm−2 across a broad pH range (8–14). The electrochemical testing of the Bi-MOF was supplemented by surface and structural characterizations to correlate the activity with structural features. This analysis unveiled the role of the organic framework and the reason why Bi-MOF surpasses other Bi-based catalysts, including commercial Bi2O2CO3, Bi2O3, and metallic Bi, in selectivity (FE), cell potential, and durability.These findings hold promise for further scale-up of CO2 reduction to formate using the cost-effective and easily prepared Bi-MOF catalyst.[1] Bienen, F., Kopljar, D., Löwe, A., Aßmann, P., Stoll, M., Rößner, P., Wagner, N., Friedrich, A., & Klemm, E. (2019). Utilizing Formate as an Energy Carrier by Coupling CO2 Electrolysis with Fuel Cell Devices. Chemie Ingenieur Technik, 91(6), 872-882.[2] Hosseini-Benhangi, P., Gyenge, C., & Gyenge, E. (2021). The carbon dioxide redox flow battery: Bifunctional CO2 reduction/formate oxidation electrocatalysis on binary and ternary catalysts. Journal of Power Sources, 495, 229752.[3] Masel, R. I., Liu, Z., Yang, H., Kaczur, J. J., Carrillo, D., Ren, S., Salvatore, D., & Berlinguette, C. P. (2021). An industrial perspective on catalysts for low-temperature CO2 electrolysis. Nature Nanotechnology, 16(2), 118-128.[4] Zou, J., Liang, G., Lee, C., & Wallace, G. G. (2023). Progress and perspectives for electrochemical CO2 reduction to formate. Materials Today Energy, 38, 101433.[5] Mazari, S. A., Hossain, N., Basirun, W. J., Mubarak, N. M., Abro, R., Sabzoi, N., & Shah, A. (2021). An overview of catalytic conversion of CO2 into fuels and chemicals using metal organic frameworks. Process Safety and Environmental Protection, 149, 67-92.[6] Xie, W., Mulina, O. M., O., A., & He, L. (2023). Metal–Organic Frameworks for Electrocatalytic CO2 Reduction into Formic Acid. Catalysts, 13(7), 1109.[7] Köppen, M., Dhakshinamoorthy, A., Inge, A.K., Cheung, O., Ångström, J., Mayer, P. and Stock, N. (2018), Synthesis, Transformation, Catalysis, and Gas Sorption Investigations on the Bismuth Metal–Organic Framework CAU-17. Eur. J. Inorg. Chem., 2018: 3496-3503.[8] Selva-Ochoa, A.G., Habibzadeh F., Gyenge E.L. (2023). Manuscript in preparation. Department of Chemical & Biological Engineering, UBC.

Photocatalytic reduction of carbon dioxide (CO2) presents a pivotal solution to address meteorological and ecological challenges. Currently, metal-organic frameworks (MOFs) with their crystalline porosity, adjustable structures, and diverse chemical functionalities have garnered significant attention in the realm of photocatalytic CO2 reduction. This review provides a brief introduction to CO2 reduction and MOF material and their applications in CO2 reduction. Then, it undertakes a comprehensive examination of MOFs, summarizing their key attributes, including porosity, large surface area, structural multifunctionalities, and responsiveness to visible light, along with an analysis of heterojunctions and their methods of preparation. Additionally, it elucidates the fundamental principle of photocatalysis and CO2 reduction, encompassing both half and overall reactions. Furthermore, the classification of MOF-based materials is explored, along with the proposed mechanism for CO2 reduction and an update on recent developments in this field. Finally, this review outlines the challenges and potential opportunities for utilizing MOFs in CO2 reduction, offering valuable insights to scholars seeking innovative approaches not only to enhance CO2 reduction but also to advance other photocatalytic processes.

Strategies for improving the photocatalytic performance of metal-organic frameworks for CO2 reduction: A review

Mapping out the Degree of Freedom of Hosted Enzymes in Confined Spatial Environments

Rapid growth in economy and society currently relies on fossil fuels heavily, leading to serious concern on energy sustainability and environmental pollution. This has aroused increasing interest in solar energy, which is the most abundant and green energy source. However, it remains a significant challenge in storing and harnessing solar energy due to its diurnal and seasonal fluctuation along with uneven distribution. Moreover, its energy density is relatively low; and the energy supply from traditional solar cells is time-varying. Consequently, it is difficult to synchronize the generation and usage of electricity from solar cells. In contrast, photocatalytic water splitting can convert solar energy to chemical energy, which can be stored in the form of hydrogen, an ideal energy carrier that is characteristic of cleanness and operational convenience. Also, photocatalytic CO2 reduction can transform greenhouse gas to valuable fuels. Furthermore, photocatalytic degradation of organic pollutants can decontaminate air, water, and soil. Additionally, photocatalytic disinfection and sterilization can reduce human exposure to pathogens and toxins. Therefore, photocatalysis has received extensive attention globally, becoming the hotspot and frontier across several fields, including chemistry, materials science, energy and environment engineering. In this special issue (Part 1), 2 progress reports, 12 review articles and 15 research articles have been published. Classified based on applications, 8 papers concern with hydrogen evolution, 7 papers involve CO2 reduction, 2 articles deal with pollutant decomposition, and 11 papers are related to nitrate reduction, nitrogen fixation, organic synthesis, syngas synthesis, NADH (nicotinamide adenine dinucleotide) regeneration and so on. From the materials perspective, 8 papers discuss C3N4, 4 articles involve CdS, 3 paper concern with conjugated polymers, other papers cover TiO2, CdSe, CoMn alloy, PbI2/CuI, silicon, metal-organic frameworks (MOFs), perovskite oxides, Bi2MoO6 and so on. Photocatalytic H2 production is of great interest from both theoretical and practical viewpoints because of its potential application in converting solar energy into storable chemical energy. Herein, Zhen and Xue (solr.202000440) have reviewed surface functionalization of polymeric carbon nitride at atomic and molecular levels for photocatalytic H2 production and CO2 reduction applications. Then, Yu et al. have (solr.202000372) reported enhanced photocatalytic H2 production activity of g-C3N4, which are prepared by one-step crystallization and cyano-group modification. Yang and co-workers (solr.202000414) have presented the fabrication of 2D/2D CdS/MXene Schottky heterojunctions by electrostatic self-assembly and solvothermal method and their application in high-efficiency photocatalytic hydrogen production. Tang and colleagues (solr.202000281) have reported the molecular cobalt catalysts grafted on a conjugated microporous polymer for high-efficiency H2 production. Zhao et al. (solr.202000415) have prepared a CdS/MoS2 nanooctahedron heterostructure with a tight interface for enhanced photocatalytic H2 evolution and biomass upgrading. Wu's group (solr.202000474) have reported a per-6-thiol-cyclodextrin engineered [FeFe]-H2ase mimic/CdSe quantum dot assembly for effective photocatalytic H2 evolution. Xu et al. (solr.202000486) have synthesized a lignin-modified g-C3N4 nanoarchitecture with an ultrathin layered topography for efficient photocatalytic H2 production. Finally, Kwon et al. (solr.202000411) have reported a self-assembly between the CdS quantum dots and the RuO2/reduced graphene oxide nanosheets, showing enhanced photocatalytic H2 production activity. Nowadays, there is increasing interest in solutions to the increasing CO2 level in the atmosphere. Photocatalytic reduction of CO2 into storable solar fuels is an appealing strategy to simultaneously overcome both environmental problems and energy crisis. In this special issue, Wang's group (solr.202000443) has firstly discussed the active sites of catalysts for CO2 activation and conversion. Then, Liang et al. (solr.202000478) have summarized recent research progress in g-C3N4 and its composite photocatalysts for CO2 reduction. Huang's group (solr.202000430) has reviewed junction engineering for photocatalytic and photoelectrocatalytic CO2 reduction. Zhang et al. (solr.202000387) have demonstrated an all-earth-abundant photothermal silicon platform for CO2 catalysis with nearly 100% sunlight absorption ability. Jia's group (solr.202000313) has reported anchoring single-atom Ru on CdS, showing enhanced CO2 capture and charge accumulation for highly selective photothermocatalytic CO2 reduction to solar fuels. Xiang et al. (solr.202000351) have prepared an ultrathin S-scheme heterojunction based on few-layer g-C3N4 and monolayer Ti3C2Tx MXene for photocatalytic CO2 reduction. Finally, Zhang's group (solr.202000326) has reported an ultraviolet-visible-near-infrared responsive Cu2-xS/g-C3N4 composite photocatalyst and its photocatalytic CO2 reduction performance. It worth noting that significant efforts have been made to prepare high-performance photocatalysts for environment remediation including air purification, hazardous waste removal, water purification, and etc. Herein Xu et al. (solr.202000416) have fabricated a g-C3N4/NH2-UIO-66 composite photocatalyst with enhanced photocatalytic removal efficiency for hexavalent chromium. Zhu's group (solr.202000453) has reported the enhanced photocatalytic phenol degradation activity in the presence of g-C3N4/PDI (perylenetetracarboxylic diimide). Janáky and co-workers (solr.202000418) have reported the preparation of PbI2/CuI nanocomposite electrode and its solar photoelectroreduction of nitrate ions. Peng's group (solr.202000487) has summarized updated research progresses in photocatalytic nitrogen-fixation reaction over semiconductors. Su and colleagues (solr.202000444) have surveyed recent advance in the rational harnessing of photoexcited hole-electron pairs in semiconductor photocatalysts, and the application in oxidative and reductive synthetic transformations for chemical and pharmaceutical production. Ouyang's group (solr.202000488) has reported the fabrication of CoMn alloy using a metal-segregation method and its enhanced photothermal conversion of syngas to light olefins. Qian and Zhang (solr.202000489) have commented the recent advance in the conjugated microporous polymers in visible light promoted chemical transformations such as water splitting, CO2 reduction, organic photoredox reactions, and etc. Chen and colleague (solr.202000442) have reviewed the current research status of Bi2MoO6-based photocatalysts and their surface/interface modification strategies and applications. Dong and co-workers (solr.202000419) have reviewed the synthesis strategy, interfacial effect and photocatalytic application of perovskite nanocrystals-based heterostructure photocatalysts. Hao and Li (solr.202000454) have reviewed visible-light initiated synergistic/cascade reactions over metal-organic frameworks. Ma's group (solr.202000397) has highlighted the 2D/2D Z-Scheme heterojunctions for photocatalytic application. Wang et al. (solr.202000392) have reviewed two-dimensional silicon (2D Si) for catalysis and photocatalysis applications. Liu's group (solr.202000339) has summarized the key developments of conjugated photocatalytic systems for NADH (nicotinamide adenine dinucleotide) regeneration. As the guest editors, we thank all the authors for their prompt response to the paper call and their valuable contribution to this special issue. All the manuscripts were refereed through rigorous peer-review processes. We greatly appreciate the timely and conscientious evaluation of manuscripts by the reviewers. Last but not least, we are grateful to Dr. Lulu Ma, Editor of Solar RRL, for her tremendous support and dedication. Jiaguo Yu received his B.S. and M.S. in chemistry from Central China Normal University and Xi'an Jiaotong University, respectively; his Ph.D. in Materials Science from Wuhan University of Technology (WUT). In 2000, he became a Professor at WUT. His research interests include photocatalysis, adsorption, supercapacitor, electrocatalysis, formaldehyde removal and so on. He is Foreign Member of Academia Europaea (The Academy of Europe) (2020), Foreign Fellow of the European Academy of Sciences (2020) and Fellow of the Royal Society of Chemistry (2015). Tierui Zhang is currently Professor at the Technical Institute of Physics and Chemistry, Chinese Academy of Sciences. He obtained his Ph.D. degree in Chemistry from Jilin University, China in 2003. He worked as a postdoctoral fellow in the labs of Prof. Markus Antonietti, Prof. Charl F.J. Faul, Prof. Hicham Fenniri, Prof. Z. RyanTian, Prof. Yadong Yin, and Prof. Yushan Yan. His current scientific interests focus on catalyst nanomaterials for energy conversion. Nianqiang Wu is currently Armstrong-Siadat Endowed Professor in Materials Science at University of Massachusetts Amherst, USA. He has received his Ph.D. degree in Materials Science and Engineering from Zhejiang University, China. Dr. Wu is Fellow of the Electrochemical Society (FECS) and Royal Society of Chemistry (FRSC). His research interest lies in: 1) photocatalysts and photoelectrochemical cells, 2) electrochemical energy storage, and 3) biosensing, microfluidics and photodynamic therapy.

Metal‐Organic Frameworks: Synthesis, Structures, and Applications

The utilization of renewable energy-driven CO2 conversion technology has garnered considerable attention as a potential remedy for both the energy crisis and climate change. Among various methods, the electrocatalytic CO2 reduction reaction (CO2RR) has received particular focus due to its mild reaction conditions and its ability to produce various valuable products. Specifically, formic acid holds great promise for CO2 electrolysis due to its potential for energy storage and transportation, as well as its commercial viability as indicated by techno-economic assessments. Bi, In, and Sn are several metal catalysts that have been reported for formic acid production, with Bi catalysts demonstrating favorable properties in terms of both cost-effectiveness and selective production of formic acid. However, despite efforts to enhance the intrinsic catalytic activity of Bi through methods such as nanostructuring and alloying, it has yet to achieve the desired level of performance. In light of recent findings by Nam et al. on the ability of a metal-organic framework (MOF) to regulate reaction intermediates for Ag catalyst, resulting in higher CO production, we draw inspiration from MOF's versatility and demonstrate the successful coupling of Bi with UiO-66, a Zr-MOF, to achieve higher CO2 reduction rates and thus increase formic acid production [1]. We synthesized MOF materials, UiO-66 and NH2-functionalized UiO-66 (UiO-66-NH2), and deposited Bi catalysts on the MOF structures using the NaBH4 reduction method, resulting in Bi/UiO-66 and Bi/UiO-66-NH2 samples. To compare the catalytic activity, we also synthesized Bi particle samples using the same method (Bi). Prior to CO2 reduction examination, all electrocatalysts were pre-treated in a 1.0 M KOH solution for 5 minutes, and then CO2 electrolysis was performed in a flow-cell reactor. Among the synthesized samples, Bi/UiO-66 demonstrated excellent CO2 reduction properties, exhibiting about 5 times higher current density (-220 mA/cm2) at an applied potential of -0.7 V vs. the reversible hydrogen electrode (RHE) than Bi alone (-44 mA/cm2), despite the identical electrochemically active surface area (ECSA) for both samples. On the other hand, Bi/UiO-66-NH2 showed an almost identical ECSA-normalized current density compared to Bi/UiO-66, indicating the negligible effect of NH2 functionalization on UiO-66 for CO2RR. Nevertheless, it is evident that the utilization of Zr-MOF (UiO-66) is beneficial in increasing the CO2 conversion rate of metallic Bi catalyst. To comprehend the reason behind the superior catalytic activity exhibited by the Bi/UiO-66 sample, we conducted various characterizations, such as SEM, TEM, FTIR, Raman, and XPS. Our results revealed that the structural evolution of UiO-66 occurs by the formation of carbonate-coordinated Zr-hydroxide during CO2 electrolysis, contributing to the high CO2 reduction current density. Moreover, the disappearance of the carbonate-relevant peak in the C 1s from XPS analysis after the decline in catalytic activity suggests that the carbonate species formed at Zr-MOF site, which is the captured form of CO2 molecules, play a crucial role in efficient CO2 capture and conversion. These findings suggest that Zr-MOF can be used for CO2 capture and conversion with high efficiency.[1] Nam et al., J. Am. Chem. Soc. 2020, 142, 51, 21513–21521.

The search for new robust and efficient heterogeneous photocatalysts for the reduction of CO2 has emerged as a key focus in the realm of CO2 reduction research. However, there is a significant challenge in fabricating a photocatalyst with remarkable photoreduction activity. In this context, accommodation of a photocatalytic redox-active molecular metal complex into a stable MOF framework by replacing the existing linker through post-synthetic exchange (PSE), also termed solvent-assisted ligand exchange (SALE), is a powerful tool for developing photocatalysts for CO2 reduction. Herein, we demonstrate for the first time the successful incorporation of a Ru(II) bis-terpyridine complex, [Ru(cptpy)2], into a stable ZrIV-based metal-organic framework (MOF) consisting of a naphthalene diimide (NDI) linker via SALE. The obtained MOF, Zr-NDI@Ru-tpy or Zr-NDI@Ru-tpy-m was used for photocatalytic CO2 reduction under visible light. The Zr-NDI@Ru-tpy shows an impressive CO production rate of 2449 μmol g-1 h-1 with a low hydrogen production rate of 101 μmol g-1 h-1, demonstrating a high selectivity of 97% for CO production. The turnover number (TON) for CO evolution by Zr-NDI@Ru-tpy is 123 in a photocatalytic run of 6 h. Furthermore, a plausible mechanism for CO2 conversion into CO has been proposed using photophysical and electrochemical investigation, along with in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. This study shows that the insertion of a redox-active molecular catalyst into a MOF is a promising method to produce efficient and stable photocatalysts that are also recyclable.

Rational design and engineering of efficient metal organic framework for visible light-driven photocatalytic carbon-di-oxide reduction