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Chiral Phosphoric Acids in Metal–Organic Frameworks with Enhanced Acidity and Tunable Catalytic Selectivity
Author(s) -
Chen Xu,
Jiang Hong,
Li Xu,
Hou Bang,
Gong Wei,
Wu Xiaowei,
Han Xing,
Zheng Fanfan,
Liu Yan,
Jiang Jianwen,
Cui Yong
Publication year - 2019
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201908959
Subject(s) - enantiopure drug , steric effects , phosphoric acid , chemistry , selectivity , catalysis , metal organic framework , combinatorial chemistry , imine , amine gas treating , brønsted–lowry acid–base theory , reactivity (psychology) , organic chemistry , enantioselective synthesis , medicine , alternative medicine , adsorption , pathology
Chiral phosphoric acids are incorporated into indium‐based metal–organic frameworks (In‐MOFs) by sterically preventing them from coordination. This concept leads to the synthesis of three chiral porous 3D In‐MOFs with different network topologies constructed from three enantiopure 1,1′‐biphenol‐phosphoric acid derived tetracarboxylate linkers. More importantly, all the uncoordinated phosphoric acid groups are periodically aligned within the channels and display significantly enhanced acidity compared to the non‐immobilized acids. This facilitates the Brønsted acid catalysis of asymmetric condensation/amine addition and imine reduction. The enantioselectivities can be tuned (up to >99 % ee ) by varying the substituents to achieve a nearly linear correlation with the concentrations of steric bulky groups in the MOFs. DFT calculations suggest that the framework provides a chiral confined microenvironment that dictates both selectivity and reactivity of chiral MOFs.