A Ni-Based Metal-Organic Framework with Polarizing Traits for Efficient Heterogeneous Catalysis in the Sustainable Synthesis of Oxazolidinones

Abstract

In this study, a Ni-based metal-organic framework (MOF), Ni-MOF, was synthesized from a mixture of Ni(OAc)₂ ⋅ 4H₂O, a dicarboxylate, 4,4’-(1,3,4-oxadiazole-2,5-diyl)dibenzoate (oxdz²⁻), and a bis(tridentate) ligand, (N,N’,N’’,N’’’-tetrakis(2-pyridylmethyl)-1,4-diaminoxylylene) (tpxn), under ambient conditions using greener solvents in 12 h. The framework was well-characterized using several analytical techniques. The highly crystalline Ni-MOF exhibited remarkable polarizing traits with significant uptake of CO₂ and water vapor up to 10.53 cm³ g⁻¹ and 290 cm³ g⁻¹, respectively, at 298 K. The isosteric heat of adsorption between Ni-MOF and CO₂ at zero loading was calculated to be 32.43 kJ mol⁻¹. Furthermore, utilizing its CO₂-philic and catalytic features, Ni-MOF was employed as an excellent heterogeneous catalyst (2.5 mol%) along with very low concentration of TBAB (0.02 mmol) as a co-catalyst for the synthesis of oxazolidinones via a standard three-component reaction among an epoxide, a substituted aniline, and carbon dioxide under solvent-free conditions. A wide range of oxazolidinones including three bioactive derivatives was synthesized using both diverse epoxides and aniline derivatives to demonstrate the substrate scope. The catalyst was proved to be recyclable, reusable, and stable for multiple cycles, without leaching of the metal from it. The mechanistic insights revealed that Ni-MOF polarizes all three reactants to catalyze the oxazolidinone formation.