A stable Pd@TP-POP catalyst with highly dispersed ultrafine Pd NPs confined in its organic pores was fabricated for catalytic reduction of 4-nitrophenol and transfer hydrogenation of aromatic aldehydes under very mild conditions.

The direct oxidation of alcohols to esters through a green and cost-effective strategy is a fascinating chemical synthesis route. In this study, an environmentally friendly N-doped porous carbon encapsulated Co-based nano-catalyst was prepared via a simple carbonization procedure, utilizing renewable chitosan, accessible dicyandiamide and low-cost Co(OAc)₂ as co-precursors. The obtained Co@NC-2-T catalysts were successfully used in selective oxidation of aromatic alcohols with methanol to esters under atmospheric reaction conditions. The Co@NC-2-900 catalyst (added with 2 g dicyandiamide and pyrolyzed at 900 °C) shows optimal activity and applicability and can also be reused at least six times in the oxidative esterification of aromatic alcohols with excellent stability. The presence of superoxide anion radicals in the current catalytic system was detected by the EPR method, and a possible mechanism of alcohol oxidation to ester was proposed on this basis. Thus, this study provides a facile, eco-friendly, and highly efficient catalytic system for oxidative esterification of alcohols.

A simple, efficient and recoverable palladium-based catalyst was successfully prepared by immobilizing palladium nanoparticles (Pd NPs) over hydrophobic core–hydrophilic shell structured mesoporous silica microspheres. The obtained catalyst was characterized by transmission electron microscopy (TEM), N₂ adsorption–desorption, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The as-prepared catalyst could rapidly convert phenol to cyclohexanone with 98.5% conversion and 97.1% selectivity under mild reaction conditions in the aqueous phase (1 atm H₂, 80 °C, 3 h). The excellent catalytic performance of the Pd/MS-C₃@MS-NH₂ catalyst was probably attributed to the enhanced synergistic effect between highly dispersed Pd NPs and significantly decreased phenol mass transfer resistance. In addition, it could be easily recovered by centrifugation and reused 5 times without any significant loss in activity and selectivity.