Morphology Changes of Transition-Metal-Substituted Aluminophosphate Molecular Sieve AlPO₄-5 Crystals

In this work, poly ethylene glycol (pEG) was used as a cosolvent to control the morphology of transition metal substituted aluminophosphate molecular sieve AlPO 4 -5 (AFI) crystals in the solvothermal reaction system of Al(OPr i ) 3 -H 3 PO 4 -TEA-Me-H 2 O-pEG (Me = Cr, Ti, Fe, V). In the presence of pEG molecules, the growth rate of the Me-AFI crystals along c -direction was significantly inhibited. With the increase of the volume ratio of pEG/H 2 O, the aspect ratio of hexagonal prismlike Cr-AFI crystals was gradually decreased and the tabletlike crystals were obtained. Further increasing the volume ratio of pEG/H 2 O resulted in the novel flowerlike morphology for Cr 3+ - and Fe 3+ -substituted AFI crystals and kiwi-fruit-like morphology for Ti 4+ and V 5+ substituted AFI crystals. Our studies revealed that the existence of pEG molecules and the isomorphic substitution of Al or P are important for the formation of these specific morphologies.