Silver Nanoparticles Immobilized Covalent Organic Microspheres for Hydrogenation of Nitroaromatics with Intriguing Catalytic Activity

Herein, we present a scalable and economic synthesis of covalent organic microspheres, a highly cross-linked microspherical polymer, through a single step process. The as-synthesized imine-linked microspherical polymer (TATF-COM) was successfully dressed with Ag nanoparticles and characterized by various spectroscopic-cum-analytical techniques, demonstrating high thermal and chemical stability. The potent catalytic behavior of as-prepared Ag@TATF-COM was evaluated for the catalytic hydrogenation of nitroaromatics (toxic pollutants) in water along with efficient synthesis of substituted imidazoles and exhibited intriguing catalytic activity with encouragement for reusability. The rate constant and Gibbs free energy for catalytic hydrogenation reaction were calculated to be 0.0226 s–1 and 83.702 kJ/mol, suggesting that the reaction is endothermic, endergonic, and nonspontaneous in nature. We accentuate the significance of shape specific property of COMs that provide a spherical morphology with high surface-to-volume ratio for uniform dressing of Ag nanoparticles. Moreover, we envisage a “catch–react–release” model to explain the catalytic process and investigated in light of experimental results. Thereafter, we have also studied the catalytic efficiency of Ag@TATF-COM in synthesis of substituted imidazoles and observed that as-prepared catalyst showed promising performance for organic transformations. In this, Ag@TATF-COM shows its advantage over previously published work.