ABSTRACT Covalent Organic Frameworks (COFs) are distinguished by their crystalline porosity and tunable optoelectronics, making them promising candidates for photocatalytic CO 2 reduction. Despite this potential, optimizing the intrinsic electronic structure to facilitate efficient charge separation and substrate activation remains a critical bottleneck. Here, we report a precise strategy to modulate the electronic environment of metal centers within a porphyrin‐based COF. Through an in situ linker exchange strategy on an imine‐linked precursor (Im‐COF‐366), we successfully constructed a highly stable azo‐linked framework, Azo‐COF‐366. The integration of azo (─N═N─) linkages serves to electronically regulate the cobalt center, effectively downshifting the conduction band and significantly enhancing charge carrier separation. Mechanistic interrogation via Density Functional Theory (DFT) and in situ DRIFTS reveals that the azo moiety enhances Co 3 d ‐orbital splitting to lower thermodynamic barriers, a finding corroborated by the dynamic evolution of key intermediates like *HCO 3 − and *COOH. Consequently, Azo‐COF‐366 delivers superior photocatalytic performance, achieving a CO production rate of 13.4 mmol·g − 1 ·h − 1 , which represents a dramatic improvement over the imine precursor, alongside 30% higher selectivity and exceptional chemical stability. This study establishes linker‐based charge modulation as a vital tool for tailoring COF electronic states, offering new design principles for advanced solar‐to‐fuel technologies.
Zhao et al. (Wed,) studied this question.