Synthesis of photoswitchable submicroparticles and their evaluation as ion-imprinted polymers for Pd(II) uptake

The idea of developing a system that enables modulation of the amount of Pd(II) ions bonded to a substrate upon exposure to external stimuli could open interesting prospects for application in various research fields such as sensors, catalysis, gas storage, and separation. In this context, in the present work, a photoresponsive compound was used as a functional monomer in the preparation, for the first time, of a photoresponsive ion-imprinted polymer (PIIP) for metal ion uptake. The Pd(II) template was used as a metal ion model, and the binding behavior of PIIP was evaluated under different experimental conditions. The adopted precipitation polymerization technique allowed us to obtain dispersed submicroparticles, as confirmed by the dynamic light scattering and Langmuir isotherm results. The photoisomerization capability of PIIP, with conformational changes of the polymer, was demonstrated, and an improved binding capacity for Pd(II) was observed after UV exposure of the polymer, with a maximum binding capacity approaching 22 mg g−1. Moreover, from the kinetic studies, the equilibrium binding capacity was reached within almost 3 h either in the dark or under UV irradiation. Finally, the reusability of the polymer over three cycles was demonstrated, and the ion selectivity of Pd(II)-PIIP was confirmed when other metal ions such as Ni(II) and Pb(II) were tested.