Frustrated Lewis Pairs Accelerating CO2 Reduction on Oxyhydroxide Photocatalysts with Surface Lattice Hydroxyls as a Solid-State Proton Donor

Light-driven CO2 reduction into high value-added product is a potential route to convert and store solar energy. Here, using the hydroxyls on an oxyhydroxide photocatalyst, CoGeO2(OH)(2), as solid-state proton source to reduce the CO2 into CH4 is proposed. It is found that under irradiation, the lattice hydroxyls on surface of CoGeO2(OH)(2) are oxidized by photogenerated holes, resulting in the generation of oxygen vacancies (O-Vs) and protons. The photoinduced O-Vs (Lewis acid) and its proximal surface hydroxyls (Lewis base) are more likely to form the frustrated Lewis acid-base pairs, which can capture, activate, and reduce CO2 with the assistance of protons into CH4. The surface lattice hydroxyls are able to regenerate when the catalyst is exposed to the water molecule-containing atmosphere, thus achieving a sustainable CO2 conversion. The proposed CO2 reduction by self-breathing surface hydroxyls may open a new avenue to use photocatalysis for energy conversion.