Mesoporous Titanium Phosphate Molecular Sieves with Ion-Exchange Capacity
Novel open framework molecular sieves, titanium(IV) phosphates named, i.e., TCM-7 and -8 (Toyota Composite Materials, numbers 7 and 8), with new mesoporous cationic framework topologies obtained by using both cationic and anionic surfactants are reported. The 31P MAS NMR, UV−visible absorption, and XANES data suggest the tetrahedral state of P and Ti, and stabilization of the tetrahedral state of Ti in TCM-7/8 is due to the incorporation of phosphorus (at Ti/P = 1:1) vis-à-vis the most stable octahedral state of Ti in the pure mesoporous TiO2. Mesoporous TCM-7 and -8 show anion exchange capacity due to the framework phosphonium cation and cation exchange capacity due to defective P−OH groups. The high catalytic activity in the liquid-phase partial oxidation of cyclohexene with a dilute H2O2 oxidant supports the tetrahedral coordination of Ti in these materials.