Synchrotron XRD and NMR evidence of germanium redistribution during silylation of BEC-type germanosilicate

The localization and distribution of germanium atoms in the framework positions of Ge-BEC zeolite upon silylation have been studied using synchrotron XRD and ¹⁹F NMR. The high thermal stability of Ge-BEC material synthesized using 1-benzyl-1,4-diazabicyclo[2.2.2]octane as the structure-directing agent (SDA) has been observed, enabling the preparation of calcined Ge-BEC. Unexpectedly, the inhomogeneous enrichment of double-four membered ring (d4r) subunits in the BEC structure with germanium has been observed. The interaction of germanosilicate with (NH₄)₂SiF₆ led to the selective substitution of germanium atoms in T2 and T3 positions with silicon, while fluoride anions preferably occupy positions inside d4r subunits.