Novel structural chemistry in small-pore zeolites in the low-to-intermediate pressure range

Pressure-induced hydration and accompanying volume expansion, first discovered in zeolite natrolite (Na16Al16Si24O80x16H2O) in 2002, has now been established to be a systematic property of this class of small-pore zeolite. Depending on the type of nonframework cations (Li, Ag, K, Rb, Cs, Ca, Sr, Pb, Cd), the degree of volume expansion and its onset pressure are controlled by up to 21% and in the pressure range of 0.4 - 3.0 GPa, respectively. These systematic high-pressure studies also demonstrated the unique capability of using high-resolution powder diffraction setup in the low-to-intermediate pressure range to provide in unprecedented details the varying degrees of structural and chemical changes occurring in complex materials from order-disorder transition of confined cation-water complexes and symmetry lowering from orthorhombic to monoclinic or even to triclinic space groups. One of the novel structural phenomena discovered in the systematic high-pressure investigations is the overturn of the zeolitic nanopores concomitant with the reversion of the cation-water distribution within. We will extend this unique pressure-induced chemistry to structurally more complex zeolites and MOFs (Metal-Organic Framework materials) via developing advanced high-resolution powder diffraction setup at SSRL.