SYNTHESIS AND STRUCTURE OF THE FORMATE SODALITES NA-8[ALSIO4](6)CENTER-DOT(HCOO)(2), NA-8[ALSIO4](6)CENTER-DOT(DCOO)(2) AND LI6NA2[ALSIO4](6)CENTER-DOT(HCOO)(2)

The compounds Na-8[AlSiO4](6).(HCOO)(2) and Na-8[AlSiO4](6).(DCOO)(2) have been prepared using a low-temperature solution synthesis and a lithium-containing derivative, Li6Na2[AlSiO4]6.(HCOO)(2), obtained through aqueous ion exchange. The compounds crystallise with the cubic sodalite structure in the space group P(4) over bar3$ n and profile refinement of powder X-ray data has been completed. The formate group was found to occupy a six-fold disordered site around the centre of the cage. Profile refinement of powder neutron data for the Na-8[AlSiO4](6).(DCOO)(2) sample verified this formate group position and located the hydrogen (deuterium) atom. Infrared (IR) and Raman spectroscopy have confirmed the presence of the formate ion within the framework, and the Si-29 and C-13 magic-angle spinning nuclear magnetic resonance (MAS NMR) spectra of Na-8[AlSiO4](6).(HCOO)(2) are consistent with an ordered alumino-silicate framework and the HCO2- group entrapped.