Sixteen isostructural phosphonate metal-organic frameworks with controlled Lewis acidity and chemical stability for asymmetric catalysis

Xu Chen,Yongwu Peng,Xiaochao Lin,Yan Liu,Xing Han,Yong Cui

doi:10.1038/s41467-017-02335-0

Xu Chen, Yongwu Peng + Show 4 more

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https://doi.org/10.1038/s41467-017-02335-0

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Journal: Nature Communications	Publication Date: Dec 1, 2017
Citations: 99	License type: open-access

Affiliation: Shanghai Jiao Tong University

Abstract

Heterogeneous catalysts typically lack the specific steric control and rational electronic tuning required for precise asymmetric catalysis. Here we demonstrate that a phosphonate metal–organic framework (MOF) platform that is robust enough to accommodate up to 16 different metal clusters, allowing for systematic tuning of Lewis acidity, catalytic activity and enantioselectivity. A total of 16 chiral porous MOFs, with the framework formula [M3L2(solvent)2] that have the same channel structures but different surface-isolated Lewis acid metal sites, are prepared from a single phosphono-carboxylate ligand of 1,1′-biphenol and 16 different metal ions. The phosphonate MOFs possessing tert-butyl-coated channels exhibited high thermal stability and good tolerances to boiling water, weak acid and base. The MOFs provide a versatile family of heterogeneous catalysts for asymmetric allylboration, propargylation, Friedel–Crafts alkylation and sulfoxidation with good to high enantioselectivity. In contrast, the homogeneous catalyst systems cannot catalyze the test reactions enantioselectively.

Highlights

Heterogeneous catalysts typically lack the specific steric control and rational electronic tuning required for precise asymmetric catalysis
The SBUs in metal–organic framework (MOF) have been explored for asymmetric catalysis[24,25,26,27], but satisfactory enantioselectivity was only achieved in one instance[26]
To evaluate the contribution of pore structures of the MOFs to the above asymmetric catalysis, we examined the catalytic activities of molecular metal phosphonates

Summary

Introduction

Heterogeneous catalysts typically lack the specific steric control and rational electronic tuning required for precise asymmetric catalysis. We report a strategy of combining bulky hydrophobic groups and chiral metal phosphonate catalysts to make stable MOFs as versatile asymmetric catalysts The premise of this approach was that a chiral phosphonate group would moderate the self-assembly and allow for stable yet crystalline MOF with metal nodes as chiral Lewis acids, while the hydrophobic groups could sterically shield the vulnerable M −O bonds and augment the hydrolytic stability of networks and exert stereochemical and electronic control over catalytic reactions. For this purpose, we synthesized a chiral dicarboxylate linker derived from 1,1′-biphenol phosphoric acid with pendant tert-butyl group at the 3,3′-position that coordinates with metal a Steric/electronic control.

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