ZEOLITES derive their catalytic activity from the strong acidity of protons attached to the negatively charged aluminosilicate frame-work, which makes the materials excellent proton donors. Unlike zeolites, the aluminophosphate molecular sieves1,2 are built from alternating AIO4 and PO tetrahedra and are thus electrically neutral. Much attention has therefore been devoted to the genera-tion of Br0nsted acidity in these materials by introducing het-eroatoms, such as Si, Mg, Fe, Co or Zn, to produce negatively charged frameworks3-6. Similar arguments apply to gallophos-phate molecular sieves7-10, of which cioverite9,to is a remarkable example. This extra-large-pore material contains pore openings in the form of a four-leafed clover, defined by a ring of 20 gallium and phosphorus atoms, some of which are linked to terminal hydroxyl groups. Here we use NMR, X-ray photoelectron spectroscopy (ESCA) and infrared spectroscopy to show that the P-OH groups in cloverite are localized versions of those in solid phosphoric acid, H3PO4. Cloverite is thus a strong Br0nsted acid even though no heteroatoms are present in its framework.

The synthesis of DPA-VPI-5 and TBA-VPI-5 and their phase transformation to AIPO4-8 have been studied by X-ray diffraction in situ. The synchrotron radiation-energy dispersive diffraction is shown to be able to monitor these two fast reactions in real time. The results indicate that nucleation may occur already during the aging of the synthesis gel. The different rates oftransformtion of DPA-VPI-5 and TBA-VPI-5 show that the microstructure of the two materials is different.

Stable van der Waals-bonded C60/benzene solvates were prepared using a novel crystallization technique. Solid-state NMR measurements on highly crystalline solvate under liquid benzene show that there is very little interaction between benzene and the C60 molecules and that the rotation of C60 at room temperature is not hindered. The magnetization transfer between benzene protons and local C60 molecules is highly inefficient. Three benzene species have been found in the solvate: two, nearly freely mobile, in wide and narrow porous structures, and the third constrained by C60 molecules in lattice defects. Premelting of deuterated benzene within the C60 solvate has been observed at Tm-10.5 K.

The synthesis of TBA-and DPA-VPI-5 has been studied in detail. Optimal synthesis conditions have been established using ternary composition diagrams for TBA-Al203-PzOs and DPA-Al203-PzO. Gel samples at different aging times have been examined using chemical analysis, X-ray diffraction, FT-IR, and solid-state NMR. Two reactions occur between H3P04 and pseudo-boehmite during gel aging. Interaction between the acid and the OH groups linking the pseudo-boehmite layers leads to the formation of an AI-0-P species in which A1 is 6-coordinated. A further reaction between the acid and the AI-O-P species results in the formation of a 4-coordinated A1 species. Because of the different aging conditions, the latter reaction begins much earlier in the TBA system than in the DPA system. The behavior of DPA in the synthesis gel is different from that of TBA. There is evidence that crystallization of VPI-5 proceedsvia a solid-state mechanism, and that nucleation in both systems occurs already during the aging of the gels.

Graphite oxide (GO) and its derivatives have been studied using 13C and 1H NMR. The 13C NMR lines at 60, 70, and 130 ppm are assigned to C-OH, C-O-C, and>CdC<groups in the bulk of the material, respectively. The>CdC<double bonds are relatively stable, while C-OH groups may condense to form C-O-C (ether) linkages. There are at least two magnetically inequivalent C-OH sites, and the structure does not necessarily possess long-range order. Water molecules interact very strongly with the structure. The results reveal a number of new structural features.