Abstract:

Covalent triazine frameworks (CTFs) represent an attractive family of metal-free visible light-responsive covalent organic frameworks (COFs), possessing promising characteristics such as large specific surface area, rich nitrogen content, permanent porosity, and high thermal and chemical stability for photocatalytic hydrogen production via water splitting. Nevertheless, the majority of CTFs are confronted with difficulty in chemical synthesis and generally suffer from low electric conductivity and severe photogenerated charge carrier recombination during photocatalytic hydrogen evolution reaction (HER). The hydrogen-evolving performance highly depends on the structure of π-conjugated CTFs and the synthetic methods, and controlled synthesis of well-defined nanostructures is still highly challenging. In this work, we report the organic acid-catalyzed synthesis of porous CTF nanoarchitectures templated by mesoporous silica molecular sieve SBA-15 with a highly ordered hexagonal structure. The SBA-15-templated CTF-S2 nanorods exhibited a substantial increase in photocatalytic HER efficiency, with an impressive 14-fold enhancement compared to the micro-sized bulk CTF-1 (4.1 μmol h⁻¹). This remarkable improvement in the photocatalytic HER over SBA-templated CTF-S2 nanostructure is attributed to the extended visible light absorption, accelerated charge carrier transfer and the optimized band structure.

Key words: Photocatalysis, Hydrogen evolution reaction, Covalent organic frameworks, Template synthesis, Porous structure