Charge carrier dynamics in covalent organic frameworks for photocatalytic CO₂ reduction

Charge utilization in photocatalytic CO₂ reduction in covalent organic frameworks (COFs) depends not only on generating long-lived charges but on directing them efficiently to catalytic sites. This review connects ultrafast photophysics with interfacial catalysis by examining charge generation, separation, transport, localization, and utilization across femtosecond-to-second timescales. It compares electron and hole dynamics in pristine, metalated, and hybrid COFs, highlighting the roles of framework topology, linkage chemistry, donor-acceptor organization, crystallinity, metal coordination, and interfacial coupling. Particular attention is given to distinguishing simple photoluminescence quenching or long-lived charge seperation states from productive charge transfer to CO₂-binding sites and reaction intermediates. Emerging strategies, including exciton engineering, energy transfer, spin-state control, orbital coupling, and photothermal assistance, are also discussed. These insights provide design principles for synchronizing carrier dynamics with catalytic turnover to improve the efficiency and selectivity of CO₂ photoreduction.