| 摘要 |
The invention provides a composition having the formula (I): xXO2.yY2O5, (wherein: 0.5<x<0.7; 0.3<y<0.5; X comprises one or more of silicon, titanium, germanium and zirconium; and Y comprises one or more of phosphorus, vanadium arsenic and antimony), or a hydrate thereof, in which the composition comprises more than 50 wt % or more of crystalline material.
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