Frustrated Lewis acid-basic pair in cobalt supported hydroxyapatite for selective reductive amination of biomass-derived furfural to furfurylamine

The synthesis of primary amines via reductive amination of lignocellulose-derived aldehydes is an appealing sustainable catalytic route. Herein, cobalt supported hydroxyapatite (Co/HAP) heterogeneous catalysts reported for reductive amination of furfural and achieved complete conversion with >99 % selectivity to furfurylamine under mild reaction conditions. The physiochemical characteristics of the catalysts were investigated thoroughly using XRD, N₂-desorption, NH₃/CO₂-TPD, XPS, TEM and FT-IR spectroscopic techniques to build their structural-activity relationship. The selective poisoning of active sites studies reveals that Lewis acidic and basic sites aided in the activation of the C=N bond and favored heterolytic cleavage of the H-H bond during amination. The expedient amount of Co⁰ species, improved dispersion of Co on HAP support, as well as strong metal-support interaction resulted in high furfurylamine (FAM) selectively. The catalyst with 7 wt% Co on HAP exhibited excellent activity over non-noble metal-based heterogeneous catalysts and on par activity with the precious metal-based catalysts. Furthermore, in the gram-scale synthesis of FAM also the catalyst exhibited 89 % selectivity. The catalyst sustained its reusable activity with five consecutive recycle runs with negligible loss.