Asymmetric electronic distribution induced enhancement in photocatalytic CO2-to-CH4 conversion via boron-doped covalent triazine frameworks.

Covalent triazine frameworks (CTFs) are emerging as promising platform for photocatalysis, yet their highly symmetric structure leads to significant charge recombination. Herein, we employed a facile non-metallic boron (B) modification with precisely controlled doping site to introduce asymmetric local electron distribution in CTFs, achieving a 15-fold activity enhancement for CO2-to-CH4 conversion. Calculations including frontier orbitals, dipole moments and molecular electrostatic potentials firmly demonstrated the formation of localized polarized electron regions in CTF-1 via B doping. Noteworthily, the primary coordination-activation site for CO2 molecules shifted from triazine ring to benzene ring, with increased adsorption energy (-0.21 vs. -0.55 eV) and a reduced CO2 bond angle (156° vs. 139°). Furthermore, the CO2-to-CH4 pathway was thoroughly clarified based upon the in-situ DRIFTS and energy barriers calculations, where CTF-1 followed the formate route and B-doped CTF utilized the water gas shift reaction. The introduction of B doping lowered energy barrier of *CHO formation for improving CH4 selectivity. This study offers a strategy for enhancing product selectivity by breaking the electronic symmetry of photocatalysts.