Using ab initio electronic structure calculations and grand canonical Monte Carlo simulations, we investigate the storage capacity of hydrogen molecules in potassium intercalated graphite oxide. We show that the energy of hydrogen binding between the layers of graphite is enhanced by induced dipole interactions and its strength is insensitive to the position of the hydrogen molecules. The trend of storage capacity with different geometries and chemical composition of scaffold materials is explained by equilibrium condition. We also examine the effects of contamination by guest molecules and potassiumion clustering on the storage capacity