Fluoride-free Synthesis of Germanosilicate CIT-13 and Its Inverse Sigma Transformation To Form CIT-14

Germanium-containing,
extra-large pore molecular sieve CIT-13 is
synthesized without the use of fluoride. After the removal of occluded
organics, CIT-13 obtained from fluoride-free preparation shows significant
differences from CIT-13 samples prepared in the presence of fluoride.
CIT-13 prepared using a fluoride-free method is able to undergo inverse
sigma transformation to yield CIT-14 and transforms into a CIT-5-type
germanosilicate much faster than Ge-CIT-13 of similar Si/Ge ratios
from a fluoride-containing synthesis. A Rietveld-refined structure
solution for CIT-14 reveals that this new molecular sieve possesses
12- and 8-membered ring channels. Results from 19F magic-angle
spinning (MAS) and 1H–29Si cross-polarized
MAS nuclear magnetic resonance spectroscopy reveal that CIT-13 crystallized
without fluoride has germanium siting which is different from CIT-13
synthesized in the presence of fluoride.