SEMIPOROUS MOS2 OBTAINED BY THE DECOMPOSITION OF THIOMOLYBDATE PRECURSORS

The decomposition of three different ammonium thiomolybdates (NH4)(2)M oS4 . xH(2)O,(NH4)(2)Mo2S12. xH(2)O, and (NH4)(2)Mo3S13. xH(2)O (x = 1 -2) have been studied by TG-DSC under argon. While all three thiomolyb dates decompose al around 673 K to yield nearly X-ray amorphous MoS2, the precursor (NH4)Mo3S13. xH(2)O does so in a manner distinct from th e other two precursors displaying a sharp exothermic peak in the DSC t race. We suggest that the unusual thermal behaviour of NH?42Mo3S13. xH (2)O might arise from a topochemical relation between the molecular cl uster and 2H-MoS2 as proposed previously. The porosity of the X-ray am orphous MoS2 obtained from the decomposition under vacuum of(NH4)(2)Mo 3S13. xH(2)O is unusually large and the material displays interesting sorption behaviour towards small organic molecules. This X-ray amorpho us semiporous modification of MoS, has been characterized in detail by powder X-ray diffraction, high resolution electron microscopy and fro m its extended X-ray absorption fine structure. An unusual feature of this material is the presence of bent, open-ended lamellae of MoS2, co ntrasting fullerene-like MoS2 which forms closed shells.