Photocatalytic water splitting and carbon dioxide (CO2) reduction provide promising solutions to global energy and environmental issues. In recent years, metal‐organic frameworks (MOFs), a class of ...crystalline porous solids featuring well‐defined and tailorable structures as well as high surface areas, have captured great interest toward photocatalytic water splitting and CO2 reduction. In this review, the semiconductor‐like behavior of MOFs is first discussed. We then summarize the recent advances in photocatalytic water splitting and CO2 reduction over MOF‐based materials and focus on the unique advantage of MOFs for clarifying the structure‐property relationship in photocatalysis. In addition, some representative characterization techniques have been presented to unveil the photocatalytic kinetics and reaction intermediates in MOF‐based systems. Finally, the challenges, and perspectives for future directions are proposed.
Photocatalytic water splitting and CO2 reduction provide a promising way to alleviate energy crisis and environmental issues. This review summarizes recent advances in photocatalytic water splitting and CO2 reduction over metal‐organic frameworks (MOFs). In addition, the fundamentals of the semiconductor‐like behavior of MOFs and several advanced characterization techniques to elucidate the photocatalytic process and mechanism are discussed.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The pore size enlargement and structural stability have been recognized as two crucial targets, which are rarely achieved together, in the development of metal–organic frameworks (MOFs). Herein, we ...have developed a versatile modulator‐induced defect‐formation strategy, in the presence of monocarboxylic acid as a modulator and an insufficient amount of organic ligand, successfully realizing the controllable synthesis of hierarchically porous MOFs (HP‐MOFs) with high stability and tailorable pore characters. Remarkably, the integration of high stability and large mesoporous property enables these HP‐MOFs to be important porous platforms for applications involving large molecules, especially in catalysis.
Cause and defect: Pore size enlargement and structural stability are two crucial targets but hardly achieved together in metal–organic frameworks (MOFs). A versatile modulator‐induced defect‐formation strategy has been developed to provide hierarchically porous MOFs (HP‐MOFs) with high stability and tailorable pore characters, which are important porous platforms for large‐molecule applications, especially in catalysis.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Metal-organic frameworks (MOFs) have been recognized as one of the most important classes of porous materials due to their unique attributes and chemical versatility. Unfortunately, some MOFs suffer ...from the drawback of relatively poor stability, which would limit their practical applications. In the recent past, great efforts have been invested in developing strategies to improve the stability of MOFs. In general, stable MOFs possess potential toward a broader range of applications. In this review, we summarize recent advances in the design and synthesis of stable MOFs and MOF-based materials
via de novo
synthesis and/or post-synthetic structural processing. Also, the relationships between the stability and functional applications of MOFs are highlighted, and finally, the subsisting challenges and the directions that future research in this field may take have been indicated.
This review summarizes recent advances in the design and synthesis of stable MOFs and highlights the relationships between the stability and functional applications.
Full text
Available for:
IJS, KILJ, NUK, UL, UM, UPUK
Photocatalytic water splitting requires separation of the mixed H2 and O2 products and is often hampered by the sluggish O2‐producing half reaction. An approach is now reported to address these ...issues by coupling the H2‐producing half reaction with value‐added benzylamine oxidation reaction using metal–organic framework (MOF) composites. Upon MOF photoexcitation, the electrons rapidly reduce the protons to generate H2 and the holes promote considerable benzylamine oxidation to N‐benzylbenzaldimine with high selectivity. Further experimental characterizations and theoretical calculation reveal that the highly conjugated s‐triazine strut in the MOF structure is crucial to the efficient charge separation and excellent photocatalytic activity.
A metal–organic framework (MOF) composite (Pt/PCN‐777) has been prepared to achieve efficient proton reduction and selective benzylamine oxidation simultaneously under light irradiation. The enlarged π‐conjugation in the MOF ligand has been demonstrated to be crucial for improving the separation of charge carriers and thus greatly enhanced catalytic efficiency.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Metal–organic frameworks (MOFs), also called porous coordination polymers, represent a class of crystalline porous materials built from organic linkers and metal ions/clusters. The unique features of ...MOFs, including structural diversity and tailorability as well as high surface area, etc., enable them to be a highly versatile platform for potential applications in many fields. Herein, an overview of recent developments achieved in MOF catalysis, including heterogeneous catalysis, photocatalysis, and eletrocatalysis over MOFs and MOF‐based materials, is provided. The active sites involved in the catalysts are particularly emphasized. The challenges, future trends, and prospects associated with MOFs and their related materials for catalysis are also discussed.
Metal–organic frameworks (MOFs), a class of crystalline porous materials, have allowed great progress in catalysis over the past two decades. An overview of recent developments for MOF catalysis, including heterogeneous organic reactions, photocatalysis, and electrocatalysis over MOFs and MOF‐based materials, is provided. The state‐of‐the‐art and opportunities and challenges regarding MOF‐based catalysis are also discussed.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
It remains highly desired but a great challenge to achieve atomically dispersed metals in high loadings for efficient catalysis. Now porphyrinic metal–organic frameworks (MOFs) have been synthesized ...based on a novel mixed‐ligand strategy to afford high‐content (1.76 wt %) single‐atom (SA) iron‐implanted N‐doped porous carbon (FeSA‐N‐C) via pyrolysis. Thanks to the single‐atom Fe sites, hierarchical pores, oriented mesochannels and high conductivity, the optimized FeSA‐N‐C exhibits excellent oxygen reduction activity and stability, surpassing almost all non‐noble‐metal catalysts and state‐of‐the‐art Pt/C, in both alkaline and more challenging acidic media. More far‐reaching, this MOF‐based mixed‐ligand strategy opens a novel avenue to the precise fabrication of efficient single‐atom catalysts.
Iron islands: Based on a mixed‐ligand strategy, a porphyrinic MOF was pyrolyzed to afford high‐content single‐atom iron‐implanted N‐doped porous carbon (FeSA‐N‐C). Thanks to the FeSA sites, hierarchical pores, oriented mesochannels, and high conductivity, FeSA‐N‐C exhibits excellent oxygen reduction activity and stability, surpassing almost all non‐noble‐metal catalysts and Pt/C, in both alkaline and the more challenging acidic media.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Defect engineering is a versatile approach to modulate band and electronic structures as well as materials performance. Herein, metal–organic frameworks (MOFs) featuring controlled structural ...defects, namely UiO‐66‐NH2‐X (X represents the molar equivalents of the modulator, acetic acid, with respect to the linker in synthesis), were synthesized to systematically investigate the effect of structural defects on photocatalytic properties. Remarkably, structural defects in MOFs are able to switch on the photocatalysis. The photocatalytic H2 production rate presents a volcano‐type trend with increasing structural defects, where Pt@UiO‐66‐NH2‐100 exhibits the highest activity. Ultrafast transient absorption spectroscopy unveils that UiO‐66‐NH2‐100 with moderate structural defects possesses the fastest relaxation kinetics and the highest charge separation efficiency, while excessive defects retard the relaxation and reduce charge separation efficiency.
Volcano‐type trend: A series of metal–organic frameworks (MOFs) decorated with Pt nanoparticles, Pt@UiO‐66‐NH2‐X, were fabricated with increasing levels of structural defects in the MOF to investigate how defect levels affect photocatalysis. The catalysts exhibit an impressive volcano‐type trend in H2 production, maximizing at a moderate defect level.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The built‐in electric field can be generated in the piezoelectric materials under mechanical stress. The resulting piezoelectric effect is beneficial to charge separation in photocatalysis. ...Meanwhile, the mechanical stress usually gives rise to accelerated mass transfer and enhanced catalytic activity. Unfortunately, it remains a challenge to differentiate the contribution of these two factors to catalytic performance. Herein, for the first time, isostructural metal–organic frameworks (MOFs), i.e., UiO‐66‐NH2(Zr) and UiO‐66‐NH2(Hf), are adopted for piezo‐photocatalysis. Both MOFs, featuring the same structures except for diverse Zr/Hf‐oxo clusters, possess distinctly different piezoelectric properties. Strikingly, UiO‐66‐NH2(Hf) exhibits ≈2.2 times of activity compared with that of UiO‐66‐NH2(Zr) under simultaneous light and ultrasonic irradiation, though both MOFs display similar activity in the photocatalytic H2 production without ultrasonic irradiation. Given their similar pore features and mass transfer behaviors, the activity difference is unambiguously assignable to the piezoelectric effect. As a result, the contributions of the piezoelectric effect to the piezo‐photocatalysis can be clearly distinguished owing to the stronger piezoelectric property of UiO‐66‐NH2(Hf).
Two isostructural metal–organic frameworks (MOFs) with distinctly different piezoelectric responses are used in piezo‐photocatalysis. Remarkably, the H2 production efficiency of Hf‐MOF is 2.2 times that of Zr‐MOF under simultaneous light and ultrasonic irradiation. The role of the piezoelectric effect can be distinguished owing to their similar pore features and mass transfer behaviors.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Single‐atom catalysts (SACs) have attracted tremendous interests due to their ultrahigh activity and selectivity. However, the rational control over coordination microenvironment of SACs remains a ...grand challenge. Herein, a post‐synthetic metal substitution (PSMS) strategy has been developed to fabricate single‐atom Ni catalysts with different N coordination numbers (denoted Ni‐Nx‐C) on pre‐designed N‐doped carbon derived from metal‐organic frameworks. When served for CO2 electroreduction, the obtained Ni‐N3‐C catalyst achieves CO Faradaic efficiency (FE) up to 95.6 %, much superior to that of Ni‐N4‐C. Theoretical calculations reveal that the lower Ni coordination number in Ni‐N3‐C can significantly enhance COOH* formation, thereby accelerating CO2 reduction. In addition, Ni‐N3‐C shows excellent performance in Zn–CO2 battery with ultrahigh CO FE and excellent stability. This work opens up a new and general avenue to coordination microenvironment modulation (MEM) of SACs for CO2 utilization.
A post‐synthetic metal substitution (PSMS) strategy has been developed to construct single‐atom Ni catalysts with different N coordination numbers (denoted as Ni‐Nx‐C) on defective carbon supports derived from metal‐organic frameworks. When served as an electrocatalyst, the Ni‐N3‐C catalyst, with lower N coordination number around Ni atoms, achieves superior catalytic performance for CO2 reduction.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The field of metal-organic frameworks (MOFs) has been incorrectly believed to be purely crystalline. However, non-crystalline MOFs (amorphous MOFs, MOF liquids, and MOF glasses) are starting to ...emerge as alternative materials, beyond the dictatorial domain of crystalline MOFs. Non-crystalline MOFs present many opportunities, either as novel functional materials themselves, or as vehicles to create other materials. In this extensive Review, we describe the two approaches to preparing amorphous MOFs: (1) the amorphization of crystalline MOFs and (2) the direct synthesis. Special attention is paid to the relationship between preparation method, properties and applications of amorphous MOFs. We also explore the field of MOF liquids and their applications, centering our attention to the phenomenon of melting. Finally, MOF glasses are explained. We highlight the properties and applications of the MOF glasses that are not usually found in crystalline MOFs. New related glass materials such as MOF-blends, flux melted MOFs, MOF crystal-glass composites, MOF and inorganic glass composites, and MOF glass membranes are also reviewed. We conclude the fields of amorphous MOFs, MOF liquids, and MOF glasses by presenting our thoughts on the possible future research directions.
The field of MOFs has been incorrectly believed to be purely crystalline. Herein, non-crystalline MOFs (amorphous MOFs, MOF liquids, and MOF glasses) are reviewed. Future research directions are also discussed.
PDF
