Sb2S3@carboxyl-modified COF S-scheme heterojunctions: the Sb–O–C interface enhances photocatalytic CO2 reduction performance

Abstract

The construction of S-scheme heterojunctions can greatly improve the catalytic performance of photocatalysts. In this study, LZU-1 was carboxylated and then combined with Sb₂S₃ to construct an S-scheme Sb₂S₃@COF-LC(SSLC) heterojunction with excellent photocatalytic properties, in which the H atom on the carboxyl group is substituted by Sb to form a stable Sb–O–C bond. COF-LC contains a specific quantity of nucleophilic carboxyl groups that enhance the availability of effective active sites, and the enhanced interfacial contact stability between Sb₂S₃ and COF-LC greatly improves the charge transfer efficiency. Under the synergistic action of multiple free radicals, Sb₂S₃@COF-LC-2 showed photocatalytic degradation of different pollutants (MB and MO), and the degradation rates reached 93.15% and 94.52%, respectively. It is worth mentioning that the CO formation rate is as high as 831.74 μmol g⁻¹ h⁻¹, and the Sb₂S₃@COF-LC-2 heterojunction has good cycling stability. Additionally, density functional theory (DFT) analyses reveal the charge-transfer mechanism of the S-scheme heterojunction. In this study, the interfacial photocarrier transfer and space charge separation of antimony-based heterojunctions were promoted by post-treatment of COF LZU-1 and substitution of hydrogen atoms on carboxyl groups with metal elements, which has the potential to be extended to the construction of other heterojunction photocatalysts.