Functional Groups-Dependent Tp-Based COF/MgIn2S4 S-Scheme Heterojunction for Photocatalytic Hydrogen Evolution

Abstract

An effective technique for improving the photocatalytic activity is the functional-group-oriented approach of covalent organic frameworks (COFs). However, the creation of the functional groups-dependent COF-based S-scheme heterojunction has seldom been reported. In this study, two distinct Tp-based COFs with different functional groups using a solvothermal technique, TpPa-1 with −H and TpPa-2 with −Me (methyl), respectively, is synthesized. Moreover, functional groups-dependent Tp-based COF/MgIn₂S₄ (MIS) S-scheme heterojunctions (i.e., TpPa-1/MIS and TpPa-2/MIS) are created to clarify the dynamics of photoinduced charges and boost the photocatalytic H₂ evolution. Notably, the photocatalytic H₂ evolution of the optimum TpPa-1/MIS-5% (13.16 mmol g⁻¹ h⁻¹) is 4.3 times greater than that of TpPa-2/MIS-5% (3.05 mmol g⁻¹ h⁻¹), which is attributed to the −Me functional groups in TpPa-2 that could slow down the interfacial photogenerated electron-transfer and make its surface less hydrophilic, resulting in the lower photocatalytic activity for H₂ evolution over TpPa-2/MIS-5%. On the contrary, the remarkable activity for H₂ evolution in TpPa-1/MIS-5% is associated with its fast interfacial photogenerated electron transfer from MIS to TpPa-1 due to the hydrophilic −H functional groups in TpPa-1, which induced to a stronger internal electric field motivated by the construction of S-scheme heterojunction.