Amorphous microporous molecular sieves studied by laser-polarized 129Xe NMR spectroscopy

Crystalline zeolites, ZSM-12 and ITQ-21, and their amorphous precursors presenting the same porosity, have been studied by hyperpolarized 129Xe NMR spectroscopy of adsorbed Xe. The higher chemical shifts and the smaller chemical shift variations with Xe concentration observed for the amorphous compared to the crystalline materials show that the pores exhibit a surface roughness responsible for a stronger Xe-surface interaction that occurs at the expense of Xe-Xe interaction inside the micropores.