Strong H₂ Binding and Selective Gas Adsorption within the Microporous Coordination Solid Mg₃(O₂C-C₁₀H₆-CO₂)₃

Abstract

The synthesis of Mg3(NDC)3(DEF)4 (NDC = 2,6-naphthalenedicarboxylate, DEF = N,N-diethylformamide, 1), the first porous metal-organic framework solid incorporating Mg2+ ions, is reported. Its structure consists of linear Mg3 units linked via NDC bridges to form a three-dimensional framework, featuring one-dimensional channels filled with DEF molecules. Significantly, its framework is fully analogous to that observed within Zn3(NDC)3(CH3OH)2.2DMF.H2O (2), demonstrating that Mg2+ ions can directly substitute for the heavier Zn2+ ions. Compound 1 is readily desolvated by heating at 190 degrees C to give the microporous solid Mg3(NDC)3, exhibiting a BET surface area of 190 m2/g. Adsorption isotherms measured at 77 and 87 K indicate high H2 adsorption enthalpies in the range 7.0-9.5 kJ/mol, depending on the degree of loading. In addition, the material displays selective adsorption of H2 or O2 over N2 or CO, suggesting possible applications in gas separation technologies.