AbstractManganese oxides are one of the most valuable materials for batteries, fuel cells and catalysis. Herein, we report the change in morphology and phase of as-synthesized Mn₂O₃ by inserting Na⁺ ions. In particular, Mn₂O₃ nanoparticles were first transformed to 2 nm thin Na_0.55Mn₂O₄·1.5H₂O nanosheets and nanobelts via hydrothermal exfoliation and Na cation intercalation and finally to sub-mm ultra-long single crystalline Na₄Mn₉O₁₈ nanowires. This paper reports the morphology and phase-dependent magnetic and catalytic (CO oxidation) properties of the as-synthesized nanostructured Na intercalated Mn-based materials.