Abstract Pure and crystalline AlPO-5 with hexagonal thin-plate morphology was synthesized ionothermally in 1-ethyl-2,3-dimethylimidazolium bromide ([edmim]Br) ionic liquid as both the solvent and structure-directing agent (SDA). The resulting microcrystalline solids were characterized using various techniques. Further studies on the influence of chemical compositions and synthesis conditions in the crystallization process of AlPO-5 were also investigated. The results showed that AlPO-5 crystals with hexagonal thin-plate morphology were obtained when [edmim]Br ionic liquid was used in ionothermal treatment. The crystallinity, size and morphology of the AlPO-5 materials were also found to be strongly influenced by two major factors, chemical composition of the gel mixture and the heating time of the gel mixture.