AlCl3 always provides acidic solution in aqueous media due to coordination of H2O via deprotonation. then add NaOH(aq) solution until the solution reached pH neutral. You can also add capping ligands according your need. Finally you can remove salt (NaCl) by repeated washing. You can follow the following paper.
Article Synthesis and Characterization of Al(OH)3, Al2O3 Nanoparticl...