Cloverite

The synthesis of Cloverite is also unique in that it established the utility of HF in zeolite molecular synthesis. In the case of silicates, either hydroxide or HF serve to mineralize the silica. That is not needed in the GaP04 synthesis but the F ion plays an important role in stabilizing the structure. The fluoride ion becomes encapsulated in the D4R units. It has been suggested that fluoride ions in fact direct... 

Figure 25. Structure of Cloverite viewed along the 100 direction.

The structure of Cloverite (IZA structure code, CLO) has limited thermal stability in air, which is not surprising for gallophosphates. It has been shown that Cloverite is stable in ambient air or a vacuum up to 500°C, but if the molecular sieve is cooled below 100°C, the structure collapses (153). If the calcined Cloverite is immediately placed in hydrocarbon solvents it can be stored at RT for several months. 

The only aluminophosphate known having a 20-MR system is JDF-20 (162, 163). The structure of JDF-20 viewed along the 001 direction is shown in Fig. 27. The large 20-MR elliptical channels are 14.5 x 7.9 x 6.2 A in diameter. Like Cloverite, JDF-20 is an interrupted framework that is reflected in the formula [Al5P6024H][N(Et3)H]2.2Fl20, where there is less A1 than P. This results in four P=0 and two O-H-O groups that protrude into the pore window. There are also intersecting channels defined by 10- and 8-MR structures. 

Cloud point (CP), 75 207 24 126 Cloud seeding, silver iodide in, 22 685 Clove bud oil, 24 542 Clove buds, 23 166 Clove leaf oil, in perfumes, 78 367 Cloverite, 76 820 Cloves, 23 155 Cloxacillin, 3 33 Cloxyfonac, 73 4 It, 48 C1S03H, fatty alcohol sulfation with, 23 541. See also Chlorosulfonic acid Clupanodonic acid, physical properties, 5 33t... 

Close-packed monolayer model, M0O3, 37 7 Cloverite, xenon diffusion in, 42 14 Cluster formation, 32 343-344 Cluster modeling... 

FIGURE 7.25 The framework of the synthetic gallophosphate, cloverite, represented as shaded spheres of van der Waals radii. (From C.R.A. Catlow (ed.) (1992) Modelling of Structure and Reactivity in Zeolites, Academic... 

The physical-chemical properties of a synthetic gallophosphate molecular sieve, the 30-A supercage cloverite , have been assessed [18]. Instead of attempting to list the burgeoning number of fullerene publications, attention is drawn to the formation and characterization of fullerene-like nanocrystals of tungsten disulfide [19,20]. Preparation, characterization and utilization of carbon nanotubes have been the subject of a number of reports from several laboratories [21-27]. 

The most obvious approach to obtain controlled mesoporosity is the extension of zeolite-like three-dimensional framework structures to larger pore-sizes. Zeolite-like compounds in the micro- and mesoporous range are the aluminophosphate VPI-5, cloverite and ULP (MCM-41). These new materials are characterized by pore diameters between 1.3 nm and 20 nm. 

However, zeolite-like materials with ultralarge pores such as Cloverite (20 T, 0.6 x 1.32 nm), VPI-5 (18 T, 1.27 nm), AIPO4-8 (14 T, 0.79 x 0.87 nm) were recently synthesized. A comparison between the pore openings of zeolites and the kinetic diameter of guest molecules shows clearly that zeolites can be used for molecular sieving. It should however be stressed that these values are temperature-dependant temperature increases both the flexibility of the guest molecules and the breathing motions of the host zeolite pore mouth and framework. 

The fluoride route of synthesis seems very rich and already provided four among the six most open frameworks described up to now in the litterature in the category of microporous compounds (0 < A) VSB-1 [22] cloverite [11], ULM-5 [23] and ULM-16 [24] with tunnels limited by 24, 20,16 and 16 polyhedra respectively. These four solids are really porous, the porosity being generated by the elimination of the template either by thermal or chemical methods which preserve the inorganic framework. 

Fig. 3. Polyhedral representation of cloverite (a), ULM-18 (b), LTA (c) and Mu-2 (d) structures based on F -centered D4R units. Fluorine atoms are black spheres.

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