Mesoporous phosphates

Many mesoporous phosphates including Ti, V, Zr, Fe, and Sn phosphates have been reported. 

The hydroamination of alkenes has been performed in the presence of heterogeneous acidic catalysts such as zeolites, amorphous aluminosilicates, phosphates, mesoporous oxides, pillared interlayered clays (PILCs), amorphous oxides, acid-treated sheet silicates or NafioN-H resins. They can be used either under batch conditions or in continuous operation at high temperature (above 200°C) under high pressure (above 100 bar). 

Sarkar, A., Biswas, S.K. and Pramanik, P. (2010) Design of a new nanostructure comprising mesoporous Zr02 shell and magnetite core (Fe304 mZr02) and study of its phosphate ion separation effidency. Journal of Materials Chemistry, 20 (21), 4417—4424. 

Pt deposited on WS2-Ti02 mesoporous composites was used for visible-light production of H2 in the presence of Na2S as radical scavenger [188]. Pt-loaded mesoporous zirconium-titanium phosphates also displayed good photoactivity in hydrogen production from carbonate solution [189]. 

Kapoor, M.P., Inagaki, S.,and Yoshida, H. (2005) Novel zirconium-titanium phosphates mesoporous materials for hydrogen production by photoinduced water splitting. Journal of Physical Chemistry B, 109 (19), 9231-9238. 

Kumar, C.V. and Chaudhari A. (2003) Unusual thermal stabilities of some proteins and enzymes bound in the galleries of layered alpha-Zr(IV) phosphate/phosphonates. Microporous and Mesoporous Materials, 57,181-190. 

Mesoporous zirconia has been prepared using anionic surfactants containing reactive oxygens that could bind Zr2+ (224-226). Mesoporous zirconia was obtained using alkyl phosphate amphiphiles but they were not stable to template removal. 

Ordered mesoporous materials of compositions other than silica or silica-alumina are also accessible. Employing the micelle templating route, several oxidic mesostructures have been made. Unfortunately, the pores of many such materials collapse upon template removal by calcination. The oxides in the pore walls are often not very well condensed or suffer from reciystallization of the oxides. In some cases, even changes of the oxidation state of the metals may play a role. Stabilization of the pore walls in post-synthesis results in a material that is rather stable toward calcination. By post-synthetic treatment with phosphoric acid, stable alumina, titania, and zirconia mesophases were obtained (see [27] and references therein). The phosphoric acid results in further condensation of the pore walls and the materials can be calcined with preservation of the pore system. Not only mesoporous oxidic materials but also phosphates, sulfides, and selenides can be obtained by surfactant templating. These materials have pore systems similar to OMS materials. 

Bhaumik, A., Inagaki, S. 2001. Mesoporous titanium phosphate molecular sieves with ion-exehange capacity J Am Chem Soe 123 691-696. 

The past nearly six decades have seen a chronological progression in molecular sieve materials from the aluminosilicate zeolites to microporous silica polymorphs, microporous aluminophosphate-based polymorphs, metallosilicate and metaHo-phosphate compositions, octahedral-tetrahedral frameworks, mesoporous molecular sieves and most recently hybrid metal organic frameworks (MOFs). A brief discussion of the historical progression is reviewed here. For a more detailed description prior to 2001 the reader is referred to [1]. The robustness of the field is evident from the fact that publications and patents are steadily increasing each year. 

Bu, X., Feng, P and Stucky, G.D. (1997) Science, 278 (5346), 2080-2085 Feng, P Bu, X., and Stucky, G.D. (1997) Hydrothermal syntheses and structural characterization of zeolite analogue compounds based on cobalt phosphate. Nature, 388, 735-741 Feng, P Bu, X., Gier, T.E., and Stucky, G.D. (1998) Amine-directed syntheses and crystal structures of phosphate-based zeolite analogs. Microp. Mesoporous Mater., 23 (3-4), 221-229. 

Sinha, A.K., Sainkar, S., and Sivas-anker, S. (1999) An improved method for the synthesis of the silicoalumino-phosphate molecular sieves, SAPO-5, SAPO-11 and SAPO-31. Micropor. Mesopor. Mater., 31, 321-331. 

Spherical particles of various metal phosphate particles can be prepared by precipitation using urea as a homogeneous precipitation agent. Surface-active agents, such as SDS and CTAC, are effective in preparation of uniform-size spherical particles. The formed spherical particles are amorphous and contain OH- and H20, except cobalt phosphate particles with layered structure. These panicles are agglomerates of primary particles, and have pores of different sizes ranging from ultramicropore to mesopore. 

New directions in the preparation of framework structures of different chemical composition and of large-pore molecular sieves include the development of phosphate-containing molecular sieves and mesoporous molecular sieves. 

Meanwhile, SDA-mediated syntheses have also been used successfully in the preparation of nonsilica mesoporous metal oxides,54-60 metal sulfides,61 and metal phosphates.62,63 An account devoted to nonsiliceous mesoporous materials and the host-guest chemistry of such systems can be found in a review by Zhao and coworkers.64... 

Both aluminum oxide and zirconium oxide are catalytically interesting materials. Pure zirconium oxide is a weak acid catalyst and to increase its acid strength and thermal stability it is usually modified with anions such as phosphates. In the context of mesoporous zirconia prepared from zirconium sulfate using the S+X I+ synthesis route it was found that by ion exchanging sulfate counter-anions in the product with phosphates, thermally stable microporous zirconium oxo-phosphates could be obtained [30-32]. Thermally stable mesoporous zirconium phosphate, zirconium oxo-phosphate and sulfate were synthesized in a similar way [33, 34], The often-encountered thermal instability of transition metal oxide mesoporous materials was circumvented in these studies by delayed crystallization caused by the presence of phosphate or sulfate anions. 

Ohare et al. (1998) Aluminum phosphates Gallium fluorophosphates Formation of mesoporous structure, intermediate phases + n.a. Synthesis optimization... 

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