Ligand geometry controlling Zn-MOF partial structures for their catalytic performance in Knoevenagel condensation

Abstract

A series of novel Zn-MOFs {1Zn: [Zn(NIA)2(3-bpdh)2]; 2Zn: [Zn(NPA)2(4-bpdh)2H2O]; 3Zn: [Zn2(CHDA)4(3-bpd)2]} were constructed by dicarboxylic acid and N,N′-bis(pyridine-yl-ethylidene)hydrazine. Ligand geometry revealed 1D to 3D Zn-MOF crystal topologies, whose combined-mode could be affected by the conditions. All these conditions affected the micro-nano crystal morphologies, namely 1Zn micro-sheets or nanospheres, 2Zn micro-clusters or micro-stick, and 3Zn micro-clusters or hollowspheres that were obtained. The catalysts exhibited 100% selectivity for Knoevenagel condensation reactions, among which the benzaldehyde conversion rate of the 3Zn hollowspheres was the highest, reaching a peak of 90%.