Tailored hydrogel entrapped catalyst with highly active, controlled catalytic activity for the removal of 4-nitrophenol (4-NP)

In catalytic reactions, achieving large specific surface area immobilisation of the catalyst is an important factor affecting the catalytic effect, however, the primary challenges in utilizing hydrogels as catalyst carriers are to enhance the mechanical properties of the hydrogel to improve the activity and controllability of the catalyst. In this study, a new structure of P(AM-co-AA)/SMA/NH2-SiO2 hydrogels was synthesized via free radical polymerization, and the effects of the content of AA and NH2-SiO2 on the mechanical properties of the hydrogels were investigated. Without the use of additional cross-linking agents, both a chemical cross-linking network and a hydrophobic linkage network were established, which effectively reconstructed the structure of the hydrogels and dissipated energy. As a result, P(AM-co-AA-1.5 %)/SMA/NH2-SiO2-0.5 % hydrogel exhibited high mechanical properties, with tensile strength, elongation, and toughness reaching 1456 KPa, 4605 %, and 23.59 MJ/m3, respectively. This hydrogel can be utilized as a template for in situ and stable Ag NPs. Additionally, P(AM-co-AA)/SMA/NH2-SiO2@Ag composite hydrogels were prepared using cation exchange and in situ reduction methods for the catalytic reduction of 4-nitrophenol (4-NP). The composite hydrogel exhibited fast catalysis, high efficiency, stable cycling, recyclability and adjustable catalytic activity at 35 °C with Kapp = 0.811 min−1. Furthermore, using this composite hydrogel alleviated the need for separating metal nanoparticle catalysts from the reaction system, thereby enabling the development of robust hydrogel materials with controlled catalytic activity for the wastewater treatment industry.