Breaking activity-transport limits in photocatalysis: 3D cyanide-rich hydrogel membranes via radical polymerization for solar-powered wastewater purification

The solar-driven degradation of organic pollutants in practical wastewater treatment is constrained not only by the intrinsic activity of photocatalysts but also by the absence of optimized catalytic systems. In this study, we devised a bifunctional K and I co-doped cyano-modified polymeric carbon nitride catalyst, which can act as a photoinitiator to enable in-situ radicals polymerization, forming a three-dimensional hydrogel photocatalytic membrane (KCN gel) under simulated sunlight. The recyclable KCN gel exhibited excellent photocatalytic performance, with the activated peroxymonosulfate (PMS) degrading organic pollutants at a rate of up to 0.438 min⁻¹, which was 18 times higher than that of the system without PMS. Theoretical calculation reveals strong van der Waals interactions between PMS and the KCN gel, with cyanide groups identified as the key active sites for methylene blue oxidation, facilitating the generation of diverse reactive species. The KCN gel displays broad applicability, effectively abating the organic contaminant across wide concentration ranges (0.1–5.0 ppm) in simulated natural waterways, offering a promising solution for sustainable wastewater treatment. © 2025 Published by Elsevier B.V.