Designing a Bifunctional Brønsted Acid–Base Heterogeneous Catalyst Through Precise Installation of Ligands on Metal–Organic Frameworks

Abstract

A Brønsted acid-base bifunctional metal-organic framework (MOF) catalyst, PCN-700-AB [A = Brønsted acid site, TPDC-(COOH) 2 [(1,1′∶4′,1″-terphenyl)-2,2″,4,4″-tetracarboxylic acid] and B = Brønsted basic site, BDC-NH 2 ], was designed precisely and synthesized successfully through sequential installation of Brønsted acid and base functionalities in a crystalline zirconium (Zr)-MOF. The installation underwent single-crystal-to-single-crystal transformation throughout the process; hence, the structure of the bifunctional catalyst could be characterized accurately via single-crystal X-ray crystallography. The bifunctional MOF catalyst obtained exhibited excellent acid-base catalytic activity for a cascade of one-pot deacetalization-Knoevenagel condensation reaction. The work presented here could be considered as a promising solution to incorporate multifunctional components readily, especially the hostile aspects, into one MOF structure.