Poly(Dehydroalanine)-Based Hydrogels as Efficient Soft Matter Matrices for Light-Driven Catalysis.

Soft matter integration of photosensitizers and catalysts provides promising solutions to developing sustainable materials for energy conversion. Particularly, hydrogels bring unique benefits as spatial control and 3D-accessiblity of molecular units as well as recyclability. Herein, we report the preparation of polyampholyte hydrogels based on poly(dehydroalanine) (PDha). Chemically-crosslinked PDha with bis-epoxy poly(ethylene glycol) lead to a transparent, self-supporting hydrogel. Due to the ionizable groups on PDha, this 3D polymeric matrix can be anionic, cationic, or zwitterionic depending on the pH, and its high density of dynamic charges has a potential for electrostatic attachment of charged molecules. We realized the integration of the cationic molecular photosensitizer [Ru(bpy) 3 ] 2+ (bpy = 2,2'-bipyridine), which is a reversible process controlled by pH, leading to light harvesting hydrogels. They were further combined with either a thiomolybdate catalyst ([Mo 3 S 13 ] -2 ) for hydrogen evolution reaction (HER) or a cobalt polyoxometalate catalyst (Co 4 POM = [Co 4 (H 2 O) 2 (PW 9 O 34 ) 2 ] 10- ) for oxygen evolution reaction (OER). Under the optimized condition, the resulting hydrogels showed catalytic activity in both case upon visible light irradiation. In case of OER, we observed higher photosensitizer stability compared to homogeneous systems, as the polymer environment seems to influence decomposition pathways. This article is protected by copyright. All rights reserved.