Copper Active Sites in Metal–Organic Frameworks Advance CO2 Adsorption and Photocatalytic Conversion

The photocatalytic reduction of CO2 into high-value chemicals utilizing solar energy represents a sustainable approach to mitigating greenhouse gas emissions and advancing renewable chemical production. Recently, copper-based metal–organic frameworks (Cu-MOFs) have been extensively researched for their potential in photocatalytic CO2 reduction, due to their high affinity for capturing CO2, the presence of unsaturated Cu sites, and their advantageous photochemical properties. In this review, we first provide an overview of Cu active sites in the secondary building units (SBUs) of MOFs, focusing on their selective adsorption of CO2 gas and analyzing the mechanisms of the multi-electron transfer processes involved in Cu-based photocatalytic reduction of CO2. Ultimately, this article outlines the existing obstacles and suggests potential avenues for future research.