In order to prove the existence of an optimum interlayer distance for H-2 uptake, we have obtained H-2 isotherms with respect to the interlayer distance of pillared-graphene oxide (GO) at 1.0 bar and 77 K. Interlayer distances of GO were changed by intercalation of three kinds of diaminoalkanes with a different number of carbon atoms (NH2(CH2)(n)NH2, n = 2, 6, 10) as pillars and changing the subsequent thermal annealing conditions. We found an optimum GO interlayer distance for maximum H-2 uptake at 6.3 angstrom similar to the predicted distance from first-principles calculations for graphitic materials, and the value obtained from thermally modulated GO. Our results experimentally corroborate the existence of an optimum interlayer distance and demonstrate the importance of an interlayer distance for the design of materials for H-2 storage. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.