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.