Sulfone-decorated hypercrosslinked polymers for sacrificial light-driven hydrogen evolution from water

Abstract

Polymer photocatalysts have emerged as a versatile class of materials for solardriven hydrogen evolution, offering tunable optoelectronic properties, structural diversity, and synthetic flexibility. Unlike inorganic semiconductors, polymer photocatalysts can be molecularly engineered to optimise light absorption, charge separation, and energy levels as well as porosity through precise control of their composition and architecture. One of the challenges of this material class is the fact that highly functionalised monomers are used, for example, multifunctional bromo and boronic acid compounds, which are then coupled using Suzuki-Miyaura polycondensation reactions that require Pd(0) catalysts. Similarly, related highly active covalent organic frameworks require highly functionalised building blocks which made using costly multi-step synthesis. Herein, we overcome this limitation of photoactive conjugated microporous polymers by preparing swellable hypercrosslinked polymers (HCPs) that combine photocatalytic activity with high accessible surface areas, which are made using inexpensive monomers and not relying on noble metals for their synthesis. The HCPs contain dibenzo [b,d]thiophene sulfone, which makes the materials photoactive and we find that the material that is made in a 2:1 ratio of 4,4′-bis(chloromethyl)-1,1′-biphenyl and dibenzo [b,d]thiophene sulfone gives the highest photocatalytic activity 249 ± 41 µmol•h -1 •g -1 .The materials appear to be unstable under photocatalytic conditions, and we are able to overcome this through the addition of a radical scavenger, which results in increased stability of the system but also increases the activity of the system to 275 ± 58 µmol h-1 g-1 . This study showcases the potential of this inexpensive and readily available material class for photocatalytic hydrogen evolution from water.