Structure and reactivity of two-dimensional silica and zeolites*

Density functional theory is applied to solve the structures of ultrathin silica and zeolite films on metal substrates based on experimental information including LEED, IR-RAS, and STM. Specifically we discuss crystalline films consisting of one or two layers of corner-sharing TO₄-tetrahedra (T=Si, Al) on Mo(112) and Ru(0001) surfaces. We also discuss the formation of amorphous phases that can be directly imaged in real space by STM, and the substitution of Si with Ti and Fe which is not isomorphous but leads to new structure types.
Joined computational – surface science studies on thin film zeolite models provide information for the limiting case of a flat surface corresponding to an infinitely large pore diameter. Whereas the non-specific adsorption energy is smaller on flat surfaces than inside zeolite pores, the acidity is significantly higher as OH frequency shifts on adsorption of molecules indicate. The consequences for understanding the acidity of layered powder materials (ZSM-5 layers) is discussed.