Precise regulation of built-in electric field over NH2-MIL-125-Ti/WO3-x S-scheme heterojunction for achieving simultaneous formation of CO and H2O2 from CO2 and H2O

[Display omitted] •A strong built-in electric field was constructed in the NH2-MIL-125(Ti)/WO3-x S-scheme heterojunction.•The oxygen vacancy content of the WO3-x was manipulated to adjust built-in electric field.•Simultaneous generation of CO and H2O2 from CO2 and H2O was realized. Manipulating the built-in electric field (BEF) is a crucial challenge in the development of efficient photocatalysts, especially for S-scheme heterojunction. Herein, a precisely regulation of the BEF intensity of an S-scheme heterojunction was realized by adjusting the oxygen vacancy (OV) content of the composed oxidation semiconductor (WO3-x nanosheets). When a moderate OV content was created in WO3-x, its Fermi level migrated down to the lowest position, resulting in the largest difference in Fermi level with the reduction semiconductor of NH2-MIL-125(Ti)(NM), and thus, the strongest BEF-driven NM/WO3-x S-scheme heterojunction was formed. The augmented BEF improved charge separation and transfer, and the S-scheme mode retained high redox ability. As a result, an efficient simultaneous production of CO (12.57 μmol⋅g−1⋅h−1) and H2O2 (8.41 μmol⋅g−1⋅h−1) from CO2 and H2O in the absence of any electron/hole sacrificial agent was achieved, which was 8.01 and 6.62 times higher compared to that of NM, respectively. This work throws inspiration for regulating BEF to enhance the carrier separation and achieve the simultaneous production from photocatalytic CO2 reduction.