Overtone Spectroscopy Of Hydrogen In Mof 5

Metal-Organic Frameworks, or MOFs, are an exciting class of nanoporous crystalline materials with applications that include hydrogen storage and hydrogen isotope separation. The dynamics of adsorbed molecular hydrogen in the prototypical material known as MOF-5 have previously been studied using infrared spectroscopy. However, the rovibrational spectrum of the isotopologues, HD and D2 were obscured due to overlap with the MOF peaks. Overtone infrared spectroscopy in conjunction with a diffuse reflectance geometry is used to observe the spectrum of H2, HD and D2. The overtone spectrum is shown to facilitate the identification of hydrogen peaks. Further, the spectrum of trapped H2 near the crystallographic metal site is greatly enhanced relative to other sites and displays a greater intensity relative to the fundamental spectrum than is seen in gas phase hydrogen. The ability of the MOF to catalyze ortho to para conversion of trapped species is also discussed.