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.