Iron oxide octahedral molecular sieve with 2x2 tunnel, designated as FeOx-OMS (2x2) was successfully synthesized by hydrothermal method. FeOx-OMS (2x2) has high degree ofpurity and higher thermal stability than those of previously reported akaganeite-type materials. The X-ray powder diffraction (XRD) pattern shows peaks that are characteristic of pure akaganeite-system. Based on its TGA profile, its thermal stability is reported up to 255 ° C. and beyond 402 °C new phases are formed which is a mixture of hematite and magnetite-based on its XRD pattern. The SEM result shows needle-like morphology that is typical of a tunnel structure.