Chitosan-starch biopolymer modified kaolin supported Pd nanoparticles for the oxidative esterification of aryl aldehydes.

A mild and efficient green protocol has been disclosed for selective oxidative esterification of various aldehydes over a novel Pd fabricated chitosan-starch polyplex encapsulated Kaolin (Kaolin@CS-starch-Pd) as a heterogeneous and reusable biocompatible nanocatalyst. Molecular oxygen was used as an oxidizing agent to generate water as the sole by-product. A wide variety of aldehydes was converted to their methyl esters in high yields. The process involved gentle reaction conditions to avoid any type of pre-activation. Structural features of the catalyst were determined through FT-IR, FE-SEM, TEM, EDX, elemental mapping, XRD and ICP-OES analyses. The material was found to be stable enough toward Pd leaching. Durability of Kaolin@CS-starch-Pd was further justified by retaining its catalytic activity through successful reusability for several times.