A simple route for the in situ preparation of catalytically active Ag nanoparticles (NPs) in hydrogel networks has been developed. The electronegativity of the amide and carboxyl groups on the poly (acrylamide-co-acryl acid) chains caused strong binding of the Ag+ ions which made the ions distribute uniformly inside the hydrogels. When the Ag+ loaded hydrogels were immersed in NaBH4 solution, the Ag+ ions on the polymer networks were reduced to Ag NPs. The resultant hydrogel showed good catalytic activity for the reduction of a common organic pollutant, 4-nitrophenol, with sodium borohydride. A kinetic study of the catalytic reaction was carried out and a possible reason for the decline of the catalytic performance with reuse is proposed. (C) 2015 Elsevier Ltd. All rights reserved.