Synthesis of isoreticular zinc(II)-phosphonocarboxylate frameworks and their application in the Friedel-Crafts benzylation reaction

摘要

Three isoreticular zinc(II)-phosphonocarboxylate frameworks, namely {[Zn3(pbdc)2]&middot2 H3O}n (ZnPC-2), {[Zn3(pbdc)2]&middotHpd&middotH 3O&middot4 H2O}n (Hpd@ZnPC-2) and {[Co 1.5Zn1.5(pbdc)2]&middot2 H3O} n (CoZnPC-2) (H4pbdc=5-phosphonobenzene-1,3-dicarboxylic acid, pd=pyrrolidine), were solvothermally synthesized. ZnPC-2 has a 3D structure based on trinuclear ZnII clusters (Zn3-SBU) showing 3D interconnected channels. Hpd@ZnPC-2 contains an isoreticular framework of ZnPC-2 with small channels blocked by Hpd molecules. In CoZnPC-2, ZnII ions in ZnPC-2 are partially substituted by CoII ions. The Friedel-Crafts benzylation reactions were carried out over these isoreticular porous materials. The catalytic results reveal that ZnPC-2 is an excellent heterogeneous Lewis acid catalyst with a high selectivity (>90 %) towards less bulky para-oriented products. The catalytic reaction has been proved to occur inside the pore of ZnPC-2, and the immobilized Zn 3-SBUs are the active sites.

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