Bridging molecular and heterogeneous catalysis: metallolinker-assembled and post-synthetically metalated covalent organic frameworks for photocatalytic CO2 reduction

Abstract

Photocatalytic carbon dioxide reduction (PCO2RR) represents a promising approach for solar-to-chemical energy conversion and carbon utilization, yet catalyst development remains limited by the trade-off between the molecular precision of homogeneous complexes and the robustness of heterogeneous materials. Metallolinker-assembled covalent organic frameworks (COFs) address this challenge by integrating well-defined metal coordination sites into crystalline porous architectures, combining tunable catalytic environments with framework stability and recyclability. Beyond acting as catalytic centers, metallolinkers regulate light harvesting, charge separation, CO2 adsorption, and local reaction environments through synergistic interactions with the surrounding framework. This review highlights recent advances in metallolinker-assembled COFs for PCO2RR and, for direct comparison, in the related family of post-synthetically metalated COFs, emphasizing how coordination chemistry, electronic structure, topology, and pore microenvironments govern catalytic activity and product selectivity. The review discusses key strategies, including metal-site modulation, linker engineering, donor–acceptor coupling, dual-site construction, and microenvironmental regulation, to elucidate structure–function relationships in CO2 activation and conversion. Remaining challenges, including operational stability, sacrificial-agent-free systems, C2+ product formation, mechanistic understanding, and scalable fabrication, are critically examined. Emerging opportunities in computational design, operando characterization, multifunctional frameworks, and device integration are further discussed to advance metallolinker-COFs toward practical solar-driven carbon conversion technologies.