Large-Pore Phosphate Structures

In recent years, enormous expansion of knowledge has taken place in the field of metal organophos-phate esters and open-framework or cavity-containing metal phosphates. Data for several hundred such compounds have been reviewed by a team of workers in this field [172]. 

Large-pore compounds with formulations suchasNiig(HP04)4(0H)3 (VSB-1) andNi2o[(OH),2(H20)g] [(HP04)s(P04)4]12H20 (VSB-5) have been described [173-176]. Zeolitic and catalytic properties have been observed in compounds of this type [177,178]. 

Many organo-templated vanadium phosphate structures have been described [163]. Templated double salts with organic anions such as acetate and oxalate are also known [179-183]. 

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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. 

Among open-framework metal phosphates, zincophosphates exhibit diverse compositions and fascinating structural topologies.[212] Notable examples are zincophosphates with extra-large pores bound by 16-, 20-, and 24-rings, and helical channels. 

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