Synthesis, Structure, and Properties of New Mg(II)-Metal–Organic Framework and Its Prowess as Catalyst in the Production of 4<i>H</i>-Pyrans

Abstract

A new alkaline metal–organic framework, [Mg3(NDC)3(DMF)4]·H2O (1) is synthesized solvothermally by using 2,6-naphthalenedicarboxylic acid (NDC) as ligand and dimethylformamide (DMF) and water as mixed solvent. Single crystal X-ray studies show that 1 crystallizes in the space group C2/c with parameters a = 13.4191(2), b = 18.0669(2), c = 20.9746(3) Å, and β = 99.66(0)o. The central metal atom Mg(II) adopts a six coordinated octahedral geometry with carboxylate oxygen atoms and DMF molecules. Due to the involvement of oxygen atoms in bridging and chelation binding, a trinuclear secondary building unit is built up, which further connects to other six NDC ligands and finally leading to a three-dimensional network. The thermal and luminescent analysis revealed that the compound is thermally stable with violet emission. The creation of coordinatively unsaturated Mg(II) centers, acting as Lewis-acidic sites upon activation, are explored to use 1 as heterogeneous catalyst in value-added organic conversions. MOF showed a superb catalytic performance in the synthesis of eight 4H-pyran derivatives via one-pot three-component reaction between aromatic aldehydes, malononitrile, and cyanoacetamide at room temperature. All the reactions worked exceptionally well with excellent yields (91–96%), in short reaction times (<40 min). Green solvent (ethanol) and easy separation, reusability and robust structure of catalyst are the attractions of the protocol and make [Mg3(NDC)3(DMF)4]·H2O an ideal catalyst for wide-ranging organic transformations.