Photoelectron migration monitored by 3d orbital electron configuration of spinel cocatalysts for covalent organic framework-based photocatalytic hydrogen evolution

Abstract

Covalent organic frameworks (COFs) are promising polymer semiconductors in solar-driven hydrogen production. It is pivotal to promote separation and transfer of charge carriers for achieving high hydrogen evolution efficiency. Herein, we presented one type of noble-metal-free photocatalytic systems by integrating typical ketoenamine-linked TpPa-COF with spinel-structured ACo2O4 (ACo2O4/TpPa-COF, A = Cu, Ni, Fe). The 3d orbital electron configurations of metal ions in ACo2O4 regulate the photogenerated electrons transfer from the conductive band of TpPa-COF to the active sites of cocatalyst. The 3d9 orbital configuration and electron-rich capability of CuCo2O4 have been evidenced to boost the directional migration of charge carriers, thus significantly expediting photocatalytic hydrogen evolution kinetics. The hydrogen evolution rate in CuCo2O4/TpPa-COF is up to 8346 µmol g−1 h−1, which surpasses those in their physical mixture (3769 µmol g−1 h−1), and is even higher than that of Pt-loaded TpPa-COF (7587 µmol g−1 h−1). This work provides new protocols to construct noble-metal-free COF-based photocatalytic systems for solar-to-chemical conversion.