Smart hydrogel-microsphere embedded silver nanoparticle catalyst with high activity and selectivity for the reduction of 4-nitrophenol and azo dyes

A simple method is reported for the preparation of silver nanoparticle (AgNP) embedded pH-responsive hydrogel microparticle catalyst via Michael addition gelation and in-situ nitrate (AgNO3) reduction. The AgNP-hydrogel microsphere exhibited an efficient reduction pollutants like 4-Nitrophenol (4-NP) Congo red (CR) under acidic medium with turn over frequency (TOF) ~170 h–1 ~124 respectively. Interestingly, activity catalysts was turned-OFF a basic (≥ pH 12) due to deswelling matrix surrounding AgNPs. On contrary, turning-OFF hydrogenation cationic pollutant methylene blue (MB) using high not possible, ionic interaction MB molecules negatively charged at this pH. This feature used demonstrate selective only from mixture 4-NP MB. Finally, five recycling steps confirmed reusability practical application potential catalyst.