Cu ion-exchanged and Cu nanoparticles decorated mesoporous ZSM-5 catalysts for the activation and utilization of phenylacetylene in a sustainable chemical synthesis

Abstract

Mesoporous ZSM-5 was synthesized using a 1,4-diazabicyclo[2.2.2]octane based multi-cationic surfactant as a structure directing agent. Cu²⁺ exchanged mesoporous ZSM-5 was prepared by the ion-exchange process. Cu nanoparticles decorated mesoporous ZSM-5 was prepared using NaBH₄ as a reducing agent. Materials were characterized by the complementary combination of X-ray diffraction, N₂-adsorption, UV-visible, and scanning/transmission electron microscopic techniques. For comparative purposes, Cu²⁺ exchanged ZSM-5, HY, and NaY; and Cu nanoparticles decorated conventional ZSM-5, SBA-15, and Al₂O₃ samples were also prepared. A sustainable catalytic process was developed for the selective synthesis of indolizine, chalcone, and triazole derivatives using a mesoporous ZSM-5 based heterogeneous catalyst. A multi-component synthetic strategy is reported here for the selective synthesis of the above mentioned chemicals that involves phenylacetylene as one of the building blocks. Control experiments were performed to ascertain the proposed reaction pathways. Recycling and leaching experiments were performed to demonstrate the sustainability and robustness of the catalytic process. Among these catalysts, Cu nanoparticles decorated mesoporous ZSM-5 exhibited the highest activity in all these reactions. The catalyst was found to be highly stable and it was possible to recycle the catalyst five times with no appreciable loss in the activity. A wide range of indolizine, chalcone, and 1,2,3-triazole derivatives were prepared in high yields using this catalyst.