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

Two isostructural MOFs {[Cd(BDC)(L)]center dot CH3OH}(n) (1) and {[Cd(NH2-BDC)(L)]center dot CH3OH}, (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 CO,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.