Efficient Visible-Light Photoreduction of CO₂ to CH₄ over an Fe-Based Metal–Organic Framework (PCN-250-Fe₃) in a Solid–Gas Mode

Solar-driven highly efficient CO2 photoreduction by water oxidation to produce high-value-added chemical feedstocks of fuels remains extremely challenging. Over the past few decades, two types of reaction modes (solid–liquid or solid–gas) have been developed by researchers to achieve substrate-based photocatlytic CO2 reduction. In the absence of organic solvents, photosensitizers, and organic sacrificial agents, the solid–gas mode may be more suitable for photocatalytic CO2 reduction. A facile hydrothermal method was used to fabricate a low-cost and photosensitive azobenzene tetracarboxylic acid-based metal–organic framework (MOF), PCN-250-Fe3, which offers the advantages of visible-light and CO2 adsorption and facilitates an electron-coupled proton transition. Notably, PCN-250-Fe3 exhibited a maximum photocatalytic activity of 16.32 μmol g–1 with ca. 77.57% selectivity in 4 h without the use of photosensitizers or organic sacrificial agents under visible-light irradiation. This photocatalytic performance is superior to that of most nonporphyrin-based MOF photocatalysts under solid–gas reaction conditions. This study provides unique insight into enhancing the efficiency of the photoreduction of CO2 to CH4 by pure water.