Formation and Structures of Hydrogen-Filled, Siliceous Zeolites at High Pressures and High Temperatures.

Solid-like nanophases of hydrogen can occur confined in porous materials under much milder pressures and temperatures than those at which bulk solid hydrogen is observed. Recent results obtained on ID27 (HC5907) showed that such nanophases in the pores of zeolites formed at high pressure and ambient temperature can be retained as metastable states in the range of 1 GPa at cryogenic temperatures. To extend this work, it is also of great interest to reduce the pressure required to form such phases, which require sufficient energy to excite ring breathing modes of the zeolite framework in order to permit H2 to enter. The goal of this proposal is to study the formation of such phases at high pressures and high temperatures by following the pore and unit cell volumes of the zeolites precisely as functions of P and T by x-ray diffraction. In this way, the P-T conditions of the formation of the swelled, H2 filled states can be determined with possible implications for H2 storage.