Schiff-base porous organic polymer-supported silver-nanoparticle, Ag0 NPs@PPTA_{- 9.08}, produces 99.3% yield of HMFCA under optimal conditions. Furthermore, a gram-scale oxidation of HMF indicates this catalytic system can be readily scaled up to an industrial level. Finally, the structural analysis indicates that the coordination of the nitrogen atom is the key factor for the higher activity and stability of Ag0 NPs@PPTA_-9.08.

Abstract

Here, a series of Schiff-base porous organic polymer-supported silver nanoparticles, Ag⁰ NPs@PPTA_-x, were prepared with a two-step ion coordination/hydrogen reduction. The resulting composite Ag⁰ NPs@PPTA_-9.08 shows excellent catalytic performance for HMF oxidation to HMFCA, and an impressive HMFCA yield of 99.3% was achieved under optimal conditions (NaOH 1.5 eq, 50 mL min⁻¹ air flow, 20 °C, 6 h). Analysis techniques such as ICP-OES, XRD, TEM, SEM, N₂ adsorption-desorption, and XPS were employed to characterize the structure and properties of Ag⁰ NPs@PPTA_-x. The results indicate that the coordination of the nitrogen atom is the key factor for the higher activity and stability of Ag⁰ NPs@PPTA_-9.08. The results of leaching and reusing tests, as well as structural characterization (XRD, SEM, and FT–IR), show that the Ag⁰ NPs@PPTA_-9.08 have good stability and robust structure. Furthermore, a gram-scale oxidation of HMF indicates this catalytic system can be readily scaled up to an industrial level. Finally, the results of other aldehydes oxidation over Ag⁰ NPs@PPTA_-9.08 indicate the good substrate adaptability of the Ag⁰ NPs@PPTA_-9.08. This work provides a new method for stabilizing nano-silver catalysts and opens up a simple avenue to the selective oxidation of aldehydes that easily scaled up.