Nano-NiCo2O4-catalyzed dehydrogenative direct esterification and amidation of primary alcohols under microwave conditions

Abstract

Here, we demonstrate NiCo₂O₄ nanoparticle-catalyzed dehydrogenative esterification and amidation of primary alcohols to esters of fatty acids and amides under microwave irradiation, without the need for any oxidant, achieving excellent yields of esters (50–92%) and amides (72–80%). The NiCo₂O₄ nanomaterial was prepared through co-precipitation, and its composition, morphology, structure, and textural properties were analyzed via powder XRD, FESEM, EDX, TEM, and BET. The crystallite size was found to be 121.69 nm using the Scherrer equation, by considering the FWHM of the (311) diffraction plane. The FESEM and EDS analysis revealed the formation of spherical-shaped granules with a mean size of 0.251 µm and their elemental composition. Furthermore, HRTEM images with a mean size of 2.25 nm confirmed the formation of spherical NiCo₂O₄ nanoparticles. The mesoporous nature of the material is analyzed by the BET surface area (33.81 m² g⁻¹) and average pore diameter 23.49 nm. The NiCo₂O₄ nanoparticles remained stable throughout the reaction process and were reusable for up to eight cycles. The catalytic nature of NiCo₂O₄ has been proved by cyclic voltametric studies of fresh and recycled catalysts. The present dehydrogenative esterification and amidation protocol offers several advantages, for example, robust and recyclable NiCo₂O₄ nanoparticles as a catalyst, oxidant- and solvent-free reaction conditions, microwave-assisted faster reaction rate, excellent isolated yields of products, etc.