SU-12: A silicon-substituted ASU-16 with circular 24-rings and templated by a monoamine

A new silicogermanate, SU-12, vertical bar(CH3CH2CH2NH3)(3)(H2O)(2.5)vertical bar[(Ge6.44Si0.56)O14.5F2], with 24-ring, channel systems was synthesized under hydro/solvothermal conditions, and its structure was determined by single-crystal X-ray diffraction. It is the first silicogermanate with extra-large 24-rings templated by a primary monoamine. Crystallographic data: tetragonal, space group I42m, unit cell parameters a = 27.6460(22) angstrom and c = 17.0885(14) angstrom, V = 13060.8(17) angstrom(3), Z = 16, rho(calcd) = 1.797 g/cm(3), R1 = 0.0512 [5471 observed reflections with I > 2 sigma(I)], wR2 = 0.1487, S (goodness-of-fit on F-2) = 1.08. SU-12 has a structure topology similar to that of the pure germanate ASU-16. However, the symmetry of SU-12 is higher than that of ASU-16, and the 24-rings become more circular than those in ASU-16. The interaction between the templates and framework is compared for ASU-16 and SU-12, and their thermal stabilities are studied. The orthorhombic ASU-16 is thermally less stable than the tetragonal SU-12 and transformed to SU-12 by heating. The ion-exchange property of SU-12 is also studied.