A Recyclable Ni(II) Metal–Organic Framework as a Catalyst for Imine Synthesis via Acceptorless Dehydrogenative Coupling and Oxidative Self-Condensation of Benzylamine

A new Ni(II) metal–organic framework (MOF), IITG-12 (IITG: Indian Institute of Technology Guwahati), was solvothermally synthesized in mixed solvents (acetonitrile and water). The as-synthesized MOF was thermally activated, followed by solvent exchange with methanol to obtain the activated MOF, namely IITG-12a. The catalytic potential of IITG-12a was explored for imine synthesis via two distinct pathways, which included oxidative coupling of benzyl alcohol and aniline derivatives through acceptorless dehydrogenation and oxidative self-condensation of benzylamine. For oxidative coupling reaction, optimal conditions are 3 mol % IITG-12a loading, KOtBu as base, toluene as solvent, 115 °C, and 8 h, with 83% isolated yield. For oxidative self-condensation of benzylamine, the optimized conditions were established as 100 °C, 24 h, under an O2 atmosphere under a solvent-free medium, delivering a yield of 96%. Both catalytic systems demonstrated a broad substrate scope with diverse functional group tolerance. The catalyst, IITG-12a, exhibited remarkable recyclability over four consecutive cycles. The stability of the catalyst after the catalytic reactions was examined via different characterization techniques. The mechanistic pathways for both transformations were studied through control experiments and reported literature analysis. This work represents the introduction of a new MOF single crystal and its catalytic applications for sustainable imines syntheses via two distinct pathways.