Ultrafine theta Al2O3 (theta-Al2O3) nanowires with average diameters of sub 10 nm and lengths up to several micrometers have been successifilly synthesized via a novel two stage method. With temperature gradually elevated, theta-Al2O3 was generated from the slow transformation of gamma-phase Al2O3 (gamma-Al2O3), and its ultrafine nanowire structure was formed from the recrystallization of gamma-Al2O3 nanowire. By means of nitrogen adsorption-desorption isotherm at 77 K and the multipoint Brunauer-Emmett-Teller (BET) method, the specific surface area of the ultrafine theta-Al2O3 nanowires is found to be up to similar to 120 m(2)/g. With the high surface area, the material displays excellent gas absorption ability. Hydrogen absorption capacities could be measured to be similar to 5.57 wt% at 77 K (liquid nitrogen), 1.51 wt% at 298 K (room temperature) and 0.81 wt% at 557 K, when a pressure of 30 atm (similar to 3 MPa) is applied. The crystal or chemical nature of metastable theta-Al2O3 phase may play a vital role in the observed excellent gas storage capacity. (c) 2013 Elsevier B.V. All rights reserved