Solvent-free microwave synthesis of 1-phenyl-1H-tetrazoles using NiTiO3/MK10 catalyst

Clay-supported green-synthesized nanoparticle-decorated heterogeneous catalysts offer an environmentally friendly and sustainable alternative to conventional homogeneous catalysts. In this work, we reported a green-synthesized NiTiO₃ nanoparticle decorated with MK10 clay surface, the composite prepared via ultrasonication method. The synthesized catalyst was used for the preparation of 1-phenyl-1H-tetrazole analogues via a microwave medium. Among the various loading percentages of the NiTiO₃/MK10 composite, 20%NiTiO₃/MK10 (M1NT20) showed good catalytic activity. The structural and morphological properties of the optimized M1NT20 heterogeneous catalyst were confirmed by various characterization techniques. The NiTiO₃ nanoparticles are evenly decorated on the surface of the MK10 clay, which was confirmed from FESEM & EDAX analysis. The average particle size and d-spacing value of the NiTiO₃ present in M1NT20 were calculated from HRTEM analysis ~ 0.295 nm and ~ 13.5 nm. The synthesized composite M1NT20 had a high surface area, and more surface-active sites were measured by BET analysis. Further, the reaction was optimized with respect to the solvent, temperature, and amount of catalyst. According to the green chemistry principle, microwave irradiation with a solvent-free system is a time-reducing and sustainable method for the synthesis of organic compounds. Synthesis of 1H-tetrazole in microwave medium presence of MINT20 heterogeneous catalyst at 60 °C under solvent-free condition shows 96% yield within 10 min and high turnover number and turnover frequency. The scale-up synthesis also showed high catalytic activity with good yield, and the recycle and reusability studies up to six cycles showed good yields.