Silver nanoparticle embedded anionic crosslinked copolymer hydrogels: an efficient catalyst

Abstract

The present study aimed to synthesize poly(2-acrylamido-2-methyl-1-propansulfonic acid-co-acrylic acid), p(AMPS-c-AA), embedded with silver nanoparticles and to investigate their potential in catalysis. The hydrogels were prepared from 2-acrylamido-2-methyl-1-propansulfonic acid (AMPS) and acrylic acid (AA) monomers via free radical polymerization reaction technique in the mild reaction condition and silver nanoparticles were fabricated within hydrogel by reducing Ag (I) ions using NaBH4 as reducing agent. The synthesized p(AMPS-c-AA) hydrogel was characterized by Fourier transform infrared (FT-IR), scanning electron microscopy (SEM) and nuclear magnetic resonance spectroscopy (NMR). Silver nanoparticles embedded in p(AMPS-c-AA) hydrogel were visualized by transmission electron microscopy (TEM). The metal content of composites was estimated via atomic absorption spectroscopy (AAS). Applications of this synthesized hydrogel was also investigated by using as a catalyst in the reduction of 4-nitrophenol and H2 generation from hydrolysis of sodium borohydride (NaBH4). The activation energies, enthalpy, and entropy for 4-NP reduction and NaBH4 hydrolysis catalyzed by composite were determined. P(AMPS-c-AA)-Ag composite was also used as catalyst in the aerobic oxidation of alcohols by emphasizing the effects of different parameters such as temperature, substituent effect, etc. Finally, recycling of the poly(AMPS-c-AA) hydrogel fabricated with Ag nanoparticles was carried out for four consecutive cycles and no significant loss in catalytic activity was observed.