Sulfonated covalent triazine polymer loaded with Pd nanoparticles as a bifunctional catalyst for one pot hydrogenation esterification reaction

Highly dispersed Pd nanoparticles over covalent triazine polymer functionalized with sulfonic acid groups (CTP-SO3H/Pd) were prepared by facile Friedel-Crafts reaction, post synthetic sulfonation and Pd immobilization method. The prepared catalyst was characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption-desorption, inductively coupled plasma - optical emission spectrometry (ICP-OES), elemental analysis and X-ray photoelectron spectroscopy (XPS). The sulfonic acid groups were grafted into the terphenyl backbone and the presence of triazine functionality within the framework enabled the uniform dispersion of palladium nanoparticles over the polymer network. When used as a bifunctional catalyst in one pot hydrogenation-esterification (OHE) reaction, the CTP-SO3H/Pd exhibited good activity and stability. The performance of CTP-SO3H/Pd is due to the surface-active acid/metal sites and was evident from the yield of the product in the reaction. The catalyst was easily recovered by filtration and recycle tests showed that it could be re-used for at least five repetitive runs with minor loss of catalytic activity suggesting its potential utility in OHE reaction. A plausible mechanistic pathway for OHE reaction over CTP-SO3H/Pd was also proposed.