Open framework

Most of the microporous and mesoporous compounds require the use of structure-directing molecules under hydro(solvo)thermal conditions [14, 15, 171, 172]. A serious handicap is the application of high-temperature calcination to develop their porosity. It usually results in inferior textural and acidic properties, and even full structural collapse occurs in the case of open frameworks, (proto) zeolites containing small-crystalline domains, and mesostructures. These materials can show very interesting properties if their structure could be fully maintained. A principal question is, is there any alternative to calcination. There is a manifested interest to find alternatives to calcination to show the potential of new structures. 

For microporous compounds with special compositions, calcination effects are even more severe. As compared with zeolites, these compounds have lower thermal stability. Strictly speaking, most of them are nonporous since removal of the occluded guest molecules by calcination usually results in collapse. This is due to strong H-bonds with the framework, coordination bonds, and sometimes the templating molecule is shared with the inorganic polyhedra. Relevant examples of low-stability microporous compounds with interesting structural features are zeolitic open-framework phosphates made of Ga [178], In [179], Zn [180], Fe [181],... 

To demonstrate the utilities of salt inclusion, we review the selected zeoUte-like transition-metal-containing open frameworks (TMCOFs) and then describe the structures of non-centrosymmetric solids (NCSs) and, finally, report crystalline solids containing a periodic array of transition metal nanostructures. In particular, we will address the issues concerning the role that molten salt has in... 

Over the last few years, we have made a number of novel discoveries using reactive salt fluxes in the crystal growth experiment of mixed-metal oxides. The most important outcome that these salt-inclusion solids have demonstrated is the propensity for structure- directing effects of the employed salt. These hybrid solids have revealed fascinating solid-state structures ranging from nanoclusters to three-dimensional open frameworks of current interest. Solids featuring mag-... 

A. K. Cheetham, G. Ferey, L. Loiseau, Inorganic materials with open frameworks. Angew. Chem. Int. Ed. 38 (1999) 3268. 

The presence of triethylenetetramine in the hydrothermal synthesis of open-framework zinc phosphates results in a number of frameworks with one- to three-dimensional structures. The structures include one-dimensional ladders, two-dimensional layer structures, and one structure where the tetramine is bound to the zinc center. The structural type was highly sensitive to the relative concentration of the amine and phosphoric acid.411 Piperazine and 2-methylpiperazine can be used as templating molecules in solvothermal syntheses of zinc phosphates. The crystallization processes of the zinc compounds were investigated by real time in situ measurements of synchrotron X-ray powder diffraction patterns.412... 

An open-framework zinc phosphate synthesized under mild hydrothermal conditions possesses two interpenetrating helical channels.414 Piperazine phosphate yields a variety of open framework structures in reaction with zinc, including linear chain, layer, and three-dimensional systems.415... 

Keywords non-isothermal kinetics, open-framework, TG analysis, SBA-3, cetyltrimethylammonium bromide (CTMAB), liquid-crystal templating. 

Fig. 9 a b Coordination mode of the outer Cu2+ ions and the Nd3+ ions at the two vertices of the huge octahedral cluster Nd6Cu24 j for 9. Symmetry codes for A and B are y, z, x and 0.5 - z, 1 — x, —0.5 + y, respectively, c Each cluster nodes link to 12 other cluster units through 12 trans-Cu(pro)2 groups, d 3D open-framework of 9. e Face-centered cubic network... 

Fig. 13 a-c Coordination mode of the outer Cu2+ ions and the Eu3+ ions at the three vertices of the huge octahedral cluster for 12. d [Er6Cu22] cluster nodes, e 3D open-framework of 12 viewed... 

Coordination Polymer Open Frameworks Constructed of Macrocyclic Complexes... 

Late Transition Metal-Oxo Compounds and Open-Framework Materials that Catalyze Aerobic Oxidations Rui Cao, Jong Woo Han, Travis M. Anderson, Daniel A. Hillesheim, Kenneth I. Hardcastle, Elena Slonkina, Britt Hedman, Keith O. Hodgson, Martin L. Kirk, Djamaladdin G. Musaev, Keiji Morokuma, Yurii V. Geletii and Craig L. Hill... 

Many of the zeolites described in Section II. A form all silica polymorphs, so it is reasonable to expect the isoelectronic germanium to form related structures. However, until recently there were relatively few examples of open framework germinates. By using an organocation as a template, a series of Ge02 molecular... 

The formula as deduced from chemical and X-ray structural analysis is Na lgSi C S There is an open framework of Si04 tetrahedra with shared corners. Some silicon ions are replaced by aluminium ions, however, and to preserve electrical neutrality sodium cations are needed. These are in excess and the overall balance is maintained by the S2, S22 and S32- ions present. Consequently, chemical formulae containing fractional proportions of elements are possible. 

LATE TRANSITION METAL-OXO COMPOUNDS AND OPEN-FRAMEWORK MATERIALS THAT CATALYZE AEROBIC OXIDATIONS... 

III. Open-Framework Materials that Catalyze Aerobic Oxidations Acknowledgments References... 

Fig. 11. Synthesis of an open-framework material, 6 (structure of 6-Gd given in Figs. 12 and 13). Condensation of a bis(triester)hexavanadate unit with the pendant triester groups terminating in carboxylic acids, 5, with lanthanide ions form the open-framework catalytic materials.

---