Construction of Polydopamine@Crosslinked Polystyrene Core/Shell Polymeric Support for the Immobilization of Silver Nano-cluster: Adsorption and Selective Reduction of p-Chloronitrobenzene.

Abstract

Polymers are promising catalyst supports because of their tunable composition and facile functionality. In this work, a core/shell polydopamine@crosslinked polystyrene support (XP-PDA) was first constructed, and silver nano-clusters were subsequently immobilized via in situ reduction to yield Ag@XP-PDA. Adsorption kinetic and temperature-dependent isotherm tests were conducted to compare the adsorption capacity of the catalysts toward the reactant p-chloronitrobenzene (P-CNB) and its corresponding hydrogenation product p-chloroaniline (P-CAN). At 298 K, Ag@XP-PDA reached adsorption equilibrium within 180 min, with distinct capacities of 38.5 mg g^-1 for P-CNB, whereas only 9.2 mg g^-1 for P-CAN. Increasing the temperature from 298 to 318 K enhanced the adsorption capacity for P-CNB (from 50.3 to 54.1 mg g^-1) while suppressing that for P-CAN (from 15.3 to 11.6 mg g^-1). This distinct temperature-dependent adsorption behavior indicates the chemisorption of P-CNB for substrate enrichment. Improved substrate adsorption and product desorption endow Ag@XP-PDA with over 90% P-CAN chemoselectivity at 318 K. Hence, the XP-PDA support enables both the stabilization of Ag nano-clusters and enrichment of the substrate, affording an efficient catalytic system for the selective reduction of P-CNB to P-CAN.