Supramolecular nanobelts assembled from tri-urea-armed thiophene derivatives as efficient metal-free photocatalysts for hydrogen evolution

Abstract

Metal-free organic photocatalysts have become a research hotspot due to their unique advantages of feasible design and structural tunability. In this study, we have designed a tri-urea group modified 1,3,5-tris(2-thienyl)benzene (TTB). The extremely strong self-assembly ability caused by rich π–π interactions and hydrogen-bonding interactions makes them assemble into nano-belt organic semiconductors. In addition, experimental and theoretical results show that the self-assembled urea-based compounds exhibit higher hydrogen evolution rates and stability, along with shorter carrier transport distances. The hydrogen evolution rate in an aqueous ascorbic acid solution under visible light irradiation reaches 505 μmol g⁻¹ h⁻¹ even without metal co-catalysts, demonstrating approximately 500-fold enhancement compared to TTB, and 50-fold enhancement compared to the unassembled catalyst. These results suggest that the self-assembly behavior plays a crucial role in enhancing photocatalytic efficiency.