HPM-2, the Layered Precursor to Zeolite MTF

Abstract

HPM-2 is a new organosilicate layered material synthesized by the fluoride route using 2-ethyl-1,3,4-trimethylimidazolium. The layers are of a new structural type (denoted mtf) and are held together by strong hydrogen bonds giving rise to a 1H magic angle spinning (MAS) nuclear magnetic resonance (NMR) at around 16 ppm and by Coulombic interactions between silanolates and the organic cations residing in the interlayer space. Upon calcination HPM-2 transforms into the pure silica MTF zeolite by topotactic condensation, a process that is essentially completed at 400 °C. Attempts to apply known methods to derive new materials (swelling, delamination, interlayer expansion) are described. In the case of the interlayer expansion reaction, a nonmicroporous dense phase is obtained, which is likely due to an unfavorable disposition of silanols in close couples within each layer. Silanol condensation between the newly incorporated silicon species occurs across the main window producing narrower (6 member ring, 6MR) rather than wider (10MR) windows.