Ab initio first-principles calculations are carried out to investigate Ti (Sc)-decorated two-dimensional boron-carbon-nitride (BC2N) sheets for their application as hydrogen storage materials. The results show that with four H-2 molecules attached to per metal atom the Ti (Sc)-decorated BC2N can store up to 7.6 wt% (7.8 wt%) of hydrogen in molecular form. The Kubas interaction and the polarization mechanism lead to the adsorption energy within the range of 0.4-0.56 eV/H-2 (0.13-0.27 eV/H-2), which is suitable for ambient temperature hydrogen storage. (C) 2012 Elsevier B. V. All rights reserved.