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.