| Research Abstract |
Zirconium phosphonates are solid materials typically synthesized in amorphous forms under aqueou conditions by the reaction of a soluble salt of a tetravalent metal and a phosphonic acid or an organophosphori acid :
However, it is possible to synthesize many of them as crystalline compounds. Preparation and characterization of two-dimensional zirconium phosphonate derivatives have been investigated. The potential applications of crystalline zirconium phosphonates have significant recent interest. Depending on the R group, different applications for these materials in the field of chromatographic separation, photochemistry, fuel cell, and catalysis are expected. In the case of zirconium phosphates, with the general formula. Zr(O_3POH)_2・nH_2O, the most extensively investigated crystalline zirconium, phosphate is an a layered acid salt, alpha-Zr(O_3POH)_2-H_2O crystallizes in the monoclinic system, as assigned by Troup and Clearfield from their single crystal work. For the zirconium phosp
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honates, however, the twodimensional tetravalent metal plane has a structure essentially similar to the zirconium phosphate structure ; substituted for hydroxyl groups are the desired organic functional groups, oriented away from the basal surfaces in a bilayered fashion in the interlayer region. Therefore, zirconium phosphonate materials can act as a series of modified surfaces, and become accessible for reactant molecules of catalysis.
Two composite zirconium phosphonates in single crystal phase have also been investigated and characterized by XRD, ^<13>C-, and ^<31>P-MASNMR. These compounds are lamellar structures comprising zirconium phosphates or organophosphonates. Each layer consists of planes of zirconium bridged through phosphonate groups which altemate above and below the Zr atom planes, oriented away from the basal surfaces in a bilayered fashion in the interlayer region. The catalytic performance over zirconium phosphonates is evaluated by hydrolysis of ethylacetate or by esterification of acefic acid. When the composite zirconium phosphonate is composed with an acidic function and with a hydrophobic function in single crystal phase, the catalytic activity showed a higher activity without swelling of the catalyst in the reaction media. The composite materials become accessible, to any reactant molecule and improve hydrophobicity. Less
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