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

A Bronsted acid-base bifunctional metal-organic framework (MOF) catalyst, PCN-700-AB [A = Bronsted acid site, TPDC-(COOH)(2) [(1,1':4',1-terphenyl)-2,2,4,4tetracarboxylic acid] and B = Bronsted basic site, BDC-NH2], was designed precisely and synthesized successfully through sequential installation of Bronsted acid and base functionalities in a crystalline zirconium (Zr)-MOF. The installation underwent single-crystal-to-singlecrystal 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.