Built-in Interface electric field microenvironment in covalent organic framework modified heterojunction guiding Electron transfer for effective photocatalytic CO reduction.

Solar-driven photocatalytic CO₂ conversion represents an innovative and eco-friendly approach to transform the predominant greenhouse gas into renewable fuels. Nevertheless, the slow movement of electron-hole pairs significantly restricts its wider practical applications. To address the challenge, our study investigates into the underlying mechanisms of the built-in electric field microenvironment, with the aim of elucidating its role in the electron transfer process. With synergistic effects stemming from its three-dimensional cross-linked porous structure and special charge-transfer pathway, triazine-based covalent organic frameworks (Tr-COFs, hereinafter referred to as COFs) were precisely anchored on lanthanum ferrate (LaFeO), forming LaFeO/COFs (LFO/COF) Z-scheme heterojunction. The LFO/COF photocatalysts exhibited excellent visible light responsive performance for CO reduction by achieving a high CO generation rate of 276.2 μmol g h with a CO selectivity of 94.4 %, significantly outperforming LaFeO and COFs alone. The significant enhancement in photocatalytic CO₂ conversion can be ascribed to the build-in electric field of the Z-scheme heterojunction, which promotes efficient charge separation. Additionally, the porous structure of LFO/COF facilitated adsorption of CO and desorption of CO. The reaction path of CO → *CO → *COOH→ *CO → CO. These results demonstrate that the interfacial electric field microenvironment is crucial for enhancing charge separation in the LFO/COF Z-scheme heterojunction, which enables efficient photocatalytic CO reduction.