Photoreduction of CO2 into sustainable and green solar fuels is generally believed to be an appealing solution to simultaneously overcome both environmental problems and energy crisis. The low selectivity of challenging multi-electron CO2 photoreduction reactions makes it one of the holy grails in heterogeneous photocatalysis. This Review highlights the important roles of cocatalysts in selective photocatalytic CO2 reduction into solar fuels using semiconductor catalysts. A special emphasis in this review is placed on the key role, design considerations and modification strategies of cocatalysts for CO2 photoreduction. Various cocatalysts, such as the biomimetic, metal-based, metal-free, and multifunctional ones, and their selectivity for CO2 photoreduction are summarized and discussed, along with the recent advances in this area. This Review provides useful information for the design of highly selective cocatalysts for photo(electro)reduction and electroreduction of CO2 and complements the existing reviews on various semiconductor photocatalysts.

Cocatalysts for Selective Photoreduction of CO2 into Solar Fuels.

Critical Aspects and Recent Advances in Structural Engineering of Photocatalysts for Sunlight-Driven Photocatalytic Reduction of CO2 into Fuels

Recent progress and remaining challenges in post-combustion CO2 capture using metal-organic frameworks (MOFs)

The development of efficient catalyst for photoredox-catalyzed selective organic synthesis has always been remaining the attractive objective in recent years. Regarding semiconductor-based photocat...

Selective Organic Transformations over Cadmium Sulfide-Based Photocatalysts

A Review of MOFs and Their Composites-Based Photocatalysts: Synthesis and Applications

Metal–organic frameworks (MOFs)1–3 are known for their specific interactions with gas molecules4,5; this, combined with their rich and ordered porosity, makes them promising candidates for the photocatalytic conversion of gas molecules to useful products6. However, attempts to use MOFs or MOF-based composites for CO2 photoreduction6–13 usually result in far lower CO2 conversion efficiency than that obtained from state-of-the-art solid-state or molecular catalysts14–18, even when facilitated by sacrificial reagents. Here we create ‘molecular compartments’ inside MOF crystals by growing TiO2 inside different pores of a chromium terephthalate-based MOF (MIL-101) and its derivatives. This allows for synergy between the light-absorbing/electron-generating TiO2 units and the catalytic metal clusters in the backbones of MOFs, and therefore facilitates photocatalytic CO2 reduction, concurrent with production of O2. An apparent quantum efficiency for CO2 photoreduction of 11.3 per cent at a wavelength of 350 nanometres is observed in a composite that consists of 42 per cent TiO2 in a MIL-101 derivative, namely, 42%-TiO2-in-MIL-101-Cr-NO2. TiO2 units in one type of compartment in this composite are estimated to be 44 times more active than those in the other type, underlining the role of precise positioning of TiO2 in this system. Investigation of a chromium-based metal–organic framework shows that the location of added TiO2 inside specific mesopores strongly affects the ability of the material to catalyse photoreduction of CO2.

Filling metal-organic framework mesopores with TiO2 for CO2 photoreduction.

Impregnation of semiconductor CdS NPs in MOFs cavities via double solvent method for effective photocatalytic CO2 conversion

Interfacial effects of MnOx-loaded TiO2 with exposed {001} facets and its catalytic activity for the photoreduction of CO2

MnOx/MIL-101 was prepared via incorporating MIL-101, a Cr(III) based MOFs, with MnOx by a photo-deposition method. Multiple techniques XRD, SEM, TEM, XPS, ESR, PL DLS were applied to investigate the structure, photocatalytic activity and mechanism of as-prepared sample. The Cr(III)-oxo clusters in MnOx/MIL-101 and MIL-101 are proposed to be responsible for visible light absorption and also act as an electron trap. MnOx/MIL-101 exhibits much higher photocatalytic activity than pure MIL-101 for degradation of RhB and MB dye under visible light irradiation and the best content of MnOx is 0.050 mol%. This is attributed to the close interaction between MIL-101 and MnOx. The holes can be transferred from MIL-101 to MnOx which is a perfect deriving-hole-types co-catalyst. This not only brings an excellent separation efficiency of the photo-generated carriers, but also another active species •OH, resulting in a higher photocatalytic activity.

Deng Ding

Papers

Filling metal-organic framework mesopores with TiO2 for CO2 photoreduction.

Impregnation of semiconductor CdS NPs in MOFs cavities via double solvent method for effective photocatalytic CO2 conversion

Interfacial effects of MnOx-loaded TiO2 with exposed {001} facets and its catalytic activity for the photoreduction of CO2

Enhanced photocatalytic activity and mechanism insight of MnO x /MIL-101

Effect of oxygen vacancies on the photocatalytic activity of flower-like BiOBr microspheres towards NO oxidation and CO2 reduction