Light driven photocatalytic hydrogen generation using BODIPY-thiophene-covalent organic polymers

Abstract

Boron-dipyrromethene (BODIPY) - based dyes have recently garnered attention as sensitizers for photocatalytic hydrogen production. They exhibit high catalytic activity through efficient electron transfer, owing to their unique properties such as high molar absorptivity, adjustable absorption and emission energies, and high fluorescence quantum efficiencies. In this study, the effect of a –OH subunit that can increase hydrophilicity on the photocatalytic hydrogen evolution in BODIPY-thiophene-based covalent organic polymers (COP) was investigated. In the conducted research, COP structures were integrated into BODIPY to enhance their light absorption capabilities, aiming to serve as photocatalysts for energy conversions under simple conditions. In the proposed system, Thiophene-BODIPY-based dyes are integrated into COP structures, where they facilitate electron excitation upon light absorption, thereby playing an effective role in photocatalytic reactions by promoting electron transfer. The photocatalyst, modified with titanium dioxide (TiO₂) nanoparticles, exhibited notable performance in enhancing the efficiency of the hydrogen production process, owing to its light absorption capabilities, multifunctional fluorescent properties, and electron-accepting characteristics. The synthesized BODIPY-Th-COP-OH_TiO₂ photocatalyst demonstrated higher hydrogen activity compared to BODIPY-Th-COP-CH₃_TiO₂, attributed to the presence of hydroxyl groups promoted hydrophilic character in the catalyst structure. Therefore, BODIPY-Th-COP-X_TiO₂ photocatalysts (X: OH, CH₃) utilizing methanol as sacrificial agent yielded hydrogen amounts of 0.197 mmol g⁻¹ h⁻¹ and 0.132 mmol g⁻¹ h⁻¹ for BODIPY-Th-COP-OH_TiO₂ and BODIPY-Th-COP-CH₃_TiO₂ photocatalysts, respectively, under visible light illumination.