zeolite VPI-5 (VFI structure) molecular sieve
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Zeolite VPI-5 (VFI structure) molecular sieve
VPI-5, whose molecular formula is (H2O)42 (AL18P18O72), is a VFI structure. Belonging to the hexagonal crystal system, it is the first ultra-large pore molecular sieve with a pore size larger than 12-membered ring. It has an 18-membered ring channel with a free aperture of 12.7*12.7A.
After dehydration of VPI-5, all AL atoms are four-coordinated, and the framework can still remain stable. VPI-5 can be converted into ALPO4-8 molecular sieve with 14-membered ring channel after calcination.