Modulated synthesis of MIL-101(Cr) in high yield and with good reproducibility using formic acid as a modulator is reported. Higher molar ratio of formic acid/CrCl3 was found to form better shape-defined MIL-101(Cr) crystals with higher surface area, larger pore volume and better hydrogen uptake performance. The highly crystalline MIL-101(Cr), composed of crystals in the size range of 100-150 nm with multifaceted surface, could be obtained in an optimized molar regime of CrCl3 center dot 6H(2)O/H2BDC/100HCOOH/550H(2)O at 210 degrees C for 8 h. The MIL-101(Cr) obtained from the modulated synthesis also showed high thermal and moisture stabilities as well as enhanced hydrogen storage capacity, making this material particularly promising for practical hydrogen storage applications. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.