Linker engineering of covalent organic frameworks for efficient photocatalytic hydrogen evolution†

Abstract

Interfacial charge transfer and active sites play important roles in the performance of heterogeneous photocatalysts. Reticular chemistry in covalent organic frameworks (COFs) allows the construction of isomeric architectures made of different donor and acceptor monomers for tuning the charge transfer dynamics and active sites. Herein, five D–A dual-pore COFs were prepared from the reaction of naphthalene-2,6-diamine (electron donor) with different tetraaldehyde electron acceptors. Experimental results disclosed that linker engineering, by changing the conjugation systems using heteroatoms of benzooxadiazole, benzothiadiazole, benzoselenadiazole, naphthothiadiazole, and naphthoselenadiazole, tuned the electron-accepting capacity of the corresponding D–A COFs. Among the five samples, the naphthothiadiazole-derived COF demonstrated optimal charge transfer and active sites, exhibiting the highest hydrogen evolution rate of ca. 35 mmol g⁻¹ h⁻¹ in the presence of 3 wt% Pt under visible-light irradiation (>420 nm). This work illustrates linker engineering as a strategy for the simultaneous adjustment of interfacial charge transfer and active sites to enhance the hydrogen generation efficiency, offering new vigor to develop the COF photocatalysts on the basis of reticular synthesis.