Constructing a novel super-crosslinked triazine COF through molecular expansion for enhanced photocatalytic performance under visible light

Abstract

A novel hyper-crosslinked triazine-based COF (HCTF-2) photocatalyst was prepared by a simple molecular expansion method. Compared with CTF-2, HCTF-2 showed excellent photocatalytic performance under visible light irradiation. The photodegradation efficiency of HCTF-2 for some pollutants (20 ppm tetracycline (TC), 30 ppm rhodamine B (RhB), 20 ppm levofloxacin hydrochloride (LEF) and 20 ppm methylene blue (MB)) can reach more than 99% in a short time. Meanwhile, HCTF-2 had a stronger hydrogen production rate (2728.61 μmol h⁻¹ g⁻¹), which was 5.11 times higher than that of CTF-2 (534.12 μmol h⁻¹ g⁻¹). Molecular oxygen activation experiments confirmed that HCTF-2 exhibited strong oxidation capacity for 3,3′,5,5′-tetramethylbenzidine (TMB), and superoxide radical and hydrogen peroxide generation ability. The photodegradation active species were identified through free radical trapping experiments and ESR. Moreover, the possible degradation pathways of LEF were analyzed by liquid chromatography-mass spectrometry (LC-MS). The enhanced photocatalytic ability of HCTF-2 was attributed to the strong absorption of visible light and the porous braided structure leading to a larger specific surface area with higher carrier separation efficiency. This research provided a strategy for the development of specially structured COFs for photocatalytic applications and more efficient improvement of photocatalytic efficiency.