NiS Nanoparticles Encapsulated in ZIF-7 as Heterogeneous Nanocomposites for the Selective Synthesis of Imines and Amines

Abstract

Herein, we have developed nickel sulphide (NiS) nanoparticles (NPs)-encapsulated Zeolitic Imidazolate Framework-7 (ZIF-7)-based nanocomposites (NiS-ZIF-7) and their application as an efficient heterogeneous catalyst for the selective synthesis of imines and amines from benzyl alcohols and aniline through simple modulation of reaction conditions. The catalytic performance of the NiS-ZIF-7 nanocomposites arises from the synergistic interaction between the NiS NPs and the ZIF-7 framework, where NiS NPs provide the catalytically active sites and the ZIF-7 framework offers a high surface area and well-defined porous channels. Based on our studies, we may conclude that imine formation occurs through acceptor-less dehydrogenative coupling (ADC), and amine formation was achieved through in situ hydrogenation of imine by borrowing hydrogen (BH) reduction mechanism. The reaction exhibited a broad substrate scope, efficiently converting electron-rich as well as electron-deficient benzyl alcohols and aniline derivatives into the corresponding imines and amines with excellent-to-good yields and characterized by ¹H and ¹³C NMR spectroscopy. Owing to its heterogeneous nature, the catalyst was recovered easily and reused up to five cycles without significant loss of catalytic activity and selectivity, highlighting its excellent stability and reusability.