Reversing V═O Orientation of Vanadyl Phthalocyanine as "Molecular Switch" on Carbon Nitride Boosts CO ₂ Photoreduction

Abstract

Abstract The precise engineering of catalytic microenvironments in single‐atom site photocatalysts is critical yet challenging for optimizing CO 2 photoreduction. Herein, we propose a novel strategy by leveraging the tunable molecular orientation of non‐planar vanadyl phthalocyanine (VOPc) as a “molecular switch” to dynamically modulate the local catalytic microenvironment. Positive surface charge and hydrogen bonding introduced by the hydroxylation of carbon nitride (C 3 N 4 ) allows a preferential “O‐down” configuration of VOPc on the modified substrate (VOPc/OH‐C 3 N 4 ). Density functional theory (DFT) calculations reveal that this specific molecular orientation lowers the energy barrier for the rate‐determining step (*CO 2 →*COOH). VOPc/OH‐C 3 N 4 shows enhanced electron transfer efficiency, an upward shift of the V‐centered d‐band toward the Fermi level, and stabilized *COOH adsorption. Consequently, VOPc/OH‐C 3 N 4 achieves a CO evolution rate of 65.22 µmol·g −1 ·h −1 , which is 7.5 times higher than that of VOPc/C 3 N 4 with “O‐up” configuration of VOPc. This work highlights that controlling the orientation of active sites presents a promising strategy for modulating interfacial electronic structures and boosting photocatalytic CO 2 reduction performance.