Effective gas adsorption and magnetic properties in a N-oxide-functionalized 3D pillared microporous Mn(Ⅱ) metal-organic framework

Abstract

N-Oxide-functional isonicotinic acid N-Oxide (HINO) ligand has been selected to construct functional metal–organic frameworks (MOFs). And based on HINO ligand and Mn(Ⅱ) center, a novel N-Oxide-functional three-dimensional (3D) pillared microporous Mn(Ⅱ)-MOF, [Mn(INO)2·CH3OH]n (1), has been constructed. MOF 1 has been characterized by single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), thermogravimetric analyses (TGA), elemental analyses (EA) and infrared spectroscopy (IR). Structural analysis reveal that in MOF 1, the N-Oxide group and carboxylic group of INO ligand connect Mn(Ⅱ) centers to form a one-dimensional (1D) Mn-O chain, and then the 1D chains are supported by INO ligands with two types of coordination modes to generate its 3D pillared microporous framework. Given the 1D Mn-O chains in MOF 1, magnetic susceptibility measurements have been conducted, which show antiferromagnetic exchange interactions between Mn(Ⅱ) centers in the Mn-O chain. Given the porosity of MOF 1 and the N-Oxide sites and vacant carboxylic O sites on its pore surfaces, gas adsorption experiments of MOF 1 have been investigated by N2, CH4 and CO2 gases. MOF 1 displays good adsorption capacity, affinity and selectivity of CO2 over CH4 and N2, indicating its potential application in postcombustion CO2 capture and gas separation.