Using sulfate-functionalized Hf-based metal-organic frameworks as a heterogeneous catalyst for solvent-free synthesis of pyrimido[1,2-a] benzimidazoles via one-pot three-component reaction

Functionalized metal-organic frameworks have recently received significant attention in heterogeneous catalysis applications due to their high catalytic activity. In this work, a sulfate-functionalized Hf-clusterbased metal-organic framework was prepared via sulfation of a Hf-MOF, named Hf-BTC, constructed by Hf-6 clusters and 1,3,5-tricarboxylate linkers. The Hf-BTC-SO4 material was consequently demonstrated to be an efficiently reusable superacid catalyst for a one-pot three-component reaction of pyrimido[1,2-a] benzimidazoles synthesis. The reaction catalyzed by the sulfated Hf-BTC could be carried out under mild and solvent-free conditions and give superior performance in a wide range of substrates. According to detailed investigation, the good catalytic performance of the sulfated-functionalized MOF likely originates from the high-porosity framework and the high active sites of the functionalized clusters. Importantly, the catalyst could be easy to recover and reuse the functionalized framework several times with minor changes in catalytic efficiency. (C) 2021 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

Automated summary

Sulfate-functionalized Hf-based metal-organic frameworks show high catalytic activity and reusability in heterogeneous catalysis applications. They possess a high-porosity framework and high active sites of functionalized clusters, enabling efficient catalysis of substrates under mild, solvent-free conditions.