Green catalytic synthesis of 5-hydroxymethyl-2-furancarboxylic acid in a gram scale over schiff base polymer supported silver-nanoparticle catalysts

Here, a series of schiff-base porous organic polymer-supported silver-nanoparticle, 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 condition (NaOH 1.5 eq, 50 mL/min 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) shows that the Ag0 NPs@PPTA-9.08 has good stability and robustness 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 selective oxidation of aldehydes that easily to scaled up.