Axially Coordinated Single‐Atom Engineering of Heterojunction Enables Multifield Synergy for Boosted H ₂ O ₂ Piezo‐Photosynthesis

ABSTRACT Photocatalysis involving proton‐coupled electron transfer offers a sustainable route for solar‐to‐chemical energy conversion, yet its efficiency and selectivity hinge on synergistically managing the photon harvesting, electron transfer, proton supply, and reactant activation. Herein, a piezoelectric S‐scheme heterojunction is constructed from Sb single atoms embedded carbon nitride and oxygen vacancy‐rich BiOIO 3 with enhanced piezoelectricity. The formed strong interfacial chemical bonds facilitate rapid and directed electron transfer between the components under the piezoelectric field. Moreover, the atomically dispersed Sb‐based frustrated Lewis pair features an electron‐deficient Sb single atom as the Lewis acid, whose acidity is enhanced by axial O coordination‐induced electron delocalization, while the adjacent electron‐rich N atom acts as the Lewis base. Such spatial and electronic structure, along with surface Brønsted acid sites, collectively establish a multi‐synergy that enhances photon absorption through the formation of hybrid energy levels, optimizes O 2 adsorption energy in the Pauling‐type configuration, and enables spontaneous hydrogenation with continuous proton supply. The heterostructure achieves a high H 2 O 2 yield rate of 5.51 mmol h −1 g −1 and selectivity of up to 99.1% without sacrificial agents. This work demonstrates a pathway for green chemical synthesis via multifield coupling and atomic‐level interface regulation.