Octahedron-based redox molecular sieves Cr-PKU-5 were synthesized by a two-step template annealing method and used as catalysts for the liquid-phase ammoximation of cyclohexanone. PKU-5 (Al4B6O15) is a novel anhydrous aluminoborate, but difficult to be synthesized due to the severe demands of preparation procedures. Interestingly, Cr-stabilized PKU-5 can be facilely prepared with nano-scaled distribution and large BET surface area by annealing Cr-doped PICU-1 precursors at high temperature. Le Bail fitting of powder XRD patterns demonstrated large amounts of Cr3+ has been incorporated into the framework of PKU-5. Much different with TS-1 redox molecular sieve, Cr-PKU-5 was favorable to produce ketazine in the liquid-phase ammoximation of ketone, rather than oxime. Based on the discussion about reaction pathway, a probable reaction mechanism was proposed to interpret the critical role of Cr-PKU-5 in such a complex multi-step reaction. (C) 2016 Elsevier B.V. All rights reserved.