Chemical reduction of metal-organic framework materials as a method to enhance gas uptake and binding

A mixed-ligand metal-organic framework (MOF) of the formula Zn-2(NDC)(2)(diPyNI) (NDC = 2,6-dicarboxylate, diPyNI = N,N'-di-(4-pyridyl)-1,4,5,8-naphthalenetetracarboxydiimide) has been chemically reduced in the solid state by lithium metal in dimethylformamide (DMF). Striking hysteresis in the N-2 adsorption isotherm suggests dynamic framework behavior of the reduced material that is not observed in the neutral MOF. The reduced framework also exhibits significantly enhanced H-2 uptake and isosteric heat of adsorption over the entire loading range. Notably, the striking increase in H-2 uptake cannot be solely attributed to H-2-Li+ interactions and is most likely augmented by increased ligand polarizability and framework displacement effects.