Comparative Effect of Amino Functionality on the Performance of Isostructural Mixed‐Ligand MOFs towards Multifunctional Catalytic Application

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Abstract
Two isostructural MOFs {[Cd(BDC)(L)] ⋅ CH3OH}n (1) and {[Cd(NH2‐BDC)(L)] ⋅ CH3OH}n (1‐NH2) involving Cd metal center and different dicarboxylate ligands (1,4‐benzenedicarboxylate (BDC) in 1 and 2‐amino‐1,4‐benzenedicarboxylate (NH2‐BDC) in 1‐NH2) and a common amide functionalized N‐donor ligand ((E)‐N′‐(pyridin‐3‐ylmethylene)nicotinohydrazide (L)) has been synthesized in bulk by diverse routes with phase‐purity. The MOFs were characterized by spectroscopic methods such as FT‐IR, elemental, TGA analysis, PXRD, and SXRD analysis. Amide functionality of L in 1 and both amide/‐NH2 functional groups attached to the ligands in 1‐NH2 of the interpenetrated isostructural 3D framework has been found to be catalytically active basic site towards multiple organic transformations. Both 1 and 1‐NH2 showed good catalytic activity towards both CO2‐epoxide cycloaddition and Biginelli reaction. A comparative study of the catalytic activity of 1 and 1‐NH2 for cycloaddition and Biginelli reaction revealed that the amine‐functionalized framework 1‐NH2 showed better catalytic performance than 1 due to the existence of additional amino site. Presence of accessible functionally decorated Lewis basic ‐NH2 and amide sites on BDC and N‐donor ligands of 1‐NH2 synergistically activate the substrate making this framework interesting and efficient heterogeneous base catalyst. Excellent product yield under moderate conditions with reusability is the highlight in both catalytic reactions.

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