Calculations based on second-order Moller–Plesset and density functional theory (DFT) methods using different exchange and correlation functionals are performed on C2H4Nb organometallic complex for its hydrogen storage capacity. We found that this complex can store up to a maximum of 14 H2 molecules using Becke-3 Lee–Yang–Parr (B3LYP)/LanL2DZ method, with a gravimetric H2 uptake capacity of 18.92 wt% and average binding energy of 0.52 eV/H2. The evaluation of the temperature dependence of the Gibbs free energy change (ΔG) of H2 adsorption process indicates that the adsorption of H2 molecules is energetically favorable below 250 K using B3LYP (LanL2DZ) and PBEPBE (LanL2MB, LanL2DZ) level of theories. On the basis of the DFT descriptors, calculated at B3LYP (LanL2DZ) and B3PW91 (LanL2MB) level of theory, we found that the stability of the complex increases with increase in the number of H2 molecules adsorbed by the complex. © 2013 Wiley Periodicals, Inc.