High pressure synthesis of novel, zeolite based nano-composite materials

Abstract

Zeolites exhibit an immense range of applications, such as those in the chemical industry, electronics and photonics among others. We used non-catalytic zeolites in an entirely new fashion. In fact, high pressure (0.5-26 GPa) chemical reactions of simple molecules in the pores of a pure SiO2 zeolite, silicalite were performed in the diamond anvil cell to obtain unique nano-composites with drastically modified properties. These materials were investigated using a combination of X-ray diffraction and optical spectroscopy. We will first show how silicalite can be easily filled by simple molecules at high pressures and how this filling deactivates pressure induced amorphization of the silica framework. We will then present a silicon carbonate phase synthesized by reacting silicalite and molecular CO2 that fills the nano-pores, at 18-26 GPa and 600-980 K; the resulting compound is slightly metastable at room pressure. On the other hand, a nano-composite, which is stable at room temperature and pressure, is obtained by photo-polymerizing ethylene at 0.5-1.5 GPa under UV (351-364 nm) irradiation in the channels of silicalite. The structure of this material is characterized by single polyethylene chains adapting very well to the confining channels, which significantly modifies the physical properties of the silicalite framework. These findings may pave the way to the high pressure synthesis of a unique generation of technological materials.