Synthesis and Characterization of CIT-13, a Germanosilicate Molecular Sieve with Extra-Large Pore Openings

Abstract

The synthesis of the germanosilicate CIT-13, a molecular sieve that is the first to have a two-dimensional (2D) pore system possessing pores that are bounded by 14- and 10-rings, is accomplished using a family of monoquaternary, benzyl-imidazolium organic structure-directing agents (OSDAs) in aqueous media containing fluoride. CIT-13 is prepared using either hydrogen fluoride (HF) or ammonium fluoride (NH4F). The structure refinement suggests that most of the Ge atoms are located in the d4r(double-4-rings) units, and that there are framework disorders in the arrangement of those d4r units. Other characterizations of CIT-13 such as Si-29 MAS NMR spectra, Ar-adsorption isotherms, and so forth are presented and compared to those of IM-12 (UTL), a previously reported germanosilicate with 14- and 12-ring pores.