MOF and COF Confined Single Active Sites for Photoreduction of CO ₂

ABSTRACT The photocatalytic conversion of CO 2 to valuable fuels is hampered by intrinsic challenges in charge separation and product selectivity. Therefore, the construction of single active sites (SASs) within metal organic frameworks (MOFs) and covalent organic frameworks (COFs) has emerged as an effective approach to address these limitations. These materials leverage well‐defined porous structures to create confined reactive microenvironments and incorporate atomically dispersed active sites that maximize metal utilization and enhance product selectivity. This review systematically summarizes recent advances in the rational design of MOF and COF confined SASs, with emphasis on key strategies, including atomic‐level engineering of active sites, modulation of the electronic and optical landscape and confinement effects, and reaction microenvironment engineering. These approaches collectively enhance light absorption, charge carrier dynamics, and intermediate stabilization. Special attention is given to the critical roles of pore confinement, local electric fields, and coordination microenvironments in steering reaction pathways and regulating key intermediates. By combining advanced in situ/operando spectroscopy with theoretical simulations, this review elucidates the fundamental structure–activity relationships governing photocatalytic behavior. Finally, this review outlines future research direction aimed at advancing MOF and COF confined SASs toward practical applications in efficient and stable CO 2 photoconversion.