Interactions of hydrogen in porous materials probed by rotational tunneling spectroscopy

A molecular-level understanding of the interactions of hydrogen at the various binding sites encountered in porous materials is of critical importance in the effort to obtain a practical material for hydrogen storage applications. One of the few molecular experimental probes available is the observation of transitions between the rotational energy levels of the bound H₂ by inelastic neutron scattering spectroscopy. The lowest of these transitions may be described as a rotational tunneling transition and its observation provides extraordinarily fine detail on the interaction of molecular hydrogen with porous host materials, as well as provide an effective interface to computational studies, whereby direction for efforts to improve hydrogen interactions with such frameworks can be derived. We will delineate some important conclusions reached in our studies on zeolites, coordination polymers, including MOF's, on, for example, the effect of charged frameworks, interpenetrating frameworks, functionalization of organic links and of open metal sites.