Hydroxyl-Bridged Phosphorus Doping-Induced Charge Polarization Enhancing Electron Delocalization for Efficient...

2D metal-free carbon nitride (CN) with extensive π-π conjugated structures suffers from electron localization due to p_z orbital overlap, which severely limits its photocatalytic CO₂ reduction performance. Herein, we propose an electron delocalization strategy via functional group-modified heteroatom doping. Through DFT screening and three-step copolymerization of phytic acid and urea, we precisely synthesized a 4-coordinated OH-bridged P-doped carbon nitride (CN-POH) featuring a unique 2N-P═OOH microstructure within heptazine units. CN-POH achieves a CO production rate of 1.82 mmol g^-1 h^-1, 15 times higher than pristine CN. Experimental and theoretical results reveal that P doping disrupts the π-π conjugation, triggering electron delocalization and transferring electrons to adjacent active N sites. The OH-modified P atom forms 2N-P═OOH coordination, inducing spatial charge polarization between VBM and CBM, which significantly enhances charge separation and electron delocalization. This unique structure also converts CO₂ adsorption from physical to chemical mode under the effect of water solvents and facilitates CO₂-to-CO conversion via hydrogen bonding with the water solvent. Collectively, CN-POH emerges as a highly efficient photocatalyst for CO₂ reduction. This work provides a promising strategy for electron delocalization in CN materials and introduces a new reaction mechanism incorporating solvent molecule interactions.