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.