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-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.
Herein,
we developed a strategy of rational constructing bimetallic
metal–organic frameworks (MOFs) and at the same time embedding
charges on backbones. Based on the Pearson’s hard/soft acid/base
(HSAB) principle, soft base (azolate) and hard base (carboxylate)
were simultaneously implanted in one building block for MOF construction,
which can preferentially coordinate with relative soft acid Cu2+ and hard acid Zr4+ (or Hf4+), respectively.
This combination during the self-assembly process not only generates
robust coordination bonds but also leaves net charges at the metal
clusters, presenting a method for rational design of bimetallic cationic
MOFs. The obtained MOF exhibits effective adsorption and release properties
selectively toward anionic dye and can also be applied outstandingly
on Cr2O7
2– removal.
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