Metal–Organic Framework (MOF) Compounds: Photocatalysts for Redox Reactions and Solar Fuel Production

Abstract

Metal-organic frameworks (MOFs) are crystalline porous materials formed from bi- or multipodal organic linkers and transition-metal nodes. Some MOFs have high structural stability, combined with large flexibility in design and post-synthetic modification. MOFs can be photoresponsive through light absorption by the organic linker or the metal oxide nodes. Photoexcitation of the light absorbing units in MOFs often generates a ligand-to-metal charge-separation state that can result in photocatalytic activity. In this Review we discuss the advantages and uniqueness that MOFs offer in photocatalysis. We present the best practices to determine photocatalytic activity in MOFs and for the deposition of co-catalysts. In particular we give examples showing the photocatalytic activity of MOFs in H2 evolution, CO2 reduction, photooxygenation, and photoreduction.

Metal–Organic‐Framework‐Based Catalysts for Photoreduction of CO2

“…[86] Both of the chargetransfer types occur in a limited range, which suggests that the semiconductivity in MOFs occurs only in a limited subset. [69,73] Inorganic semiconductors absorb a photon with the energy equal to or higher than their band gap, resulting in that a negative electron (e − ) is excited from the valence band (VB) to the conduction band (CB) and simultaneously a positive hole (h + ) is left on the VB, implying that a charge-separated state is generated. [69,73] Inorganic semiconductors absorb a photon with the energy equal to or higher than their band gap, resulting in that a negative electron (e − ) is excited from the valence band (VB) to the conduction band (CB) and simultaneously a positive hole (h + ) is left on the VB, implying that a charge-separated state is generated.…”

“…[73,108] The stability of MOFs in a long-time catalytic reaction can be investigated by powder X-ray diffraction (XRD), quantum calculations, surface area measurements, and spectroscopy techniques. The photodegradation/photodecomposition (e.g., structure collapse and decarboxylation) of organic molecules may www.advmat.de www.advancedsciencenews.com occur upon prolonged illumination.…”

“…[10] MOFs are composed of inorganic and organic components, which correspond to metal ions or clusters and organic linkers, respectively. [69][70][71][72][73][74] The high-density metal nodes provide abundant catalytic active sites. [66][67][68] Resembling inorganic semiconductors, some MOFs also show photocatalytic activity under the irradiation of UV or visible light; their metal clusters are regarded as inorganic semiconductor quantum dots and their organic linkers can be taken as antennae to harvest light and sensitize and activate these metal clusters.…”

A metal-organic cage incorporating multiple light harvesting and catalytic centres for photochemical hydrogen production

“…In this context, crystalline metal-organic frameworks (MOFs) have been widely studied in photocatalytic water splitting in heterogeneous conditions123 owing to the advantages that verstaile organic chromophores and catalytically active metal centres can be integrated into the framework, or, loaded into the pores. In contrast, the analogous metal-organic cages/containers (MOCs), which feature discrete, nanoscale metallosupramolecules with well-designed shape and size have drawn little attention for photocatalytic H 2 production, bearing in mind that MOCs have been vigorously investigated for many other reactions456789 in terms of the confined coordination space and guest-selective windows, especially with relevance to enzyme mimics.…”

Syntheses and Characterization of Three Coordination Polymers of Zinc(II) and Cadmium(II) with Dicarboxylates and Bis(thiabendazole) Ligands

“…Coordination polymers (CPs) have attracted significant research interest in academia and industry because of their diverse structures and potential applications in gas adsorption/storage, drug delivery, magnetism, luminescence and catalysis [1][2][3][4][5]. From a synthetic point of view, the judicious selection of appropriate organic ligands is proved to be one of the most effective ways to construct CPs.…”