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 Zn2(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 N2 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 H2 uptake and isosteric heat of adsorption over the entire loading range. Notably, the striking increase in H2 uptake cannot be solely attributed to H2−Li+ interactions and is most likely augmented by increased ligand polarizability and framework displacement effects.