Synthesis of MIL-102, a Chromium Carboxylate Metal−Organic Framework, with Gas Sorption Analysis

TLDR: Thermogravimetric analysis and X-ray thermodiffractometry indicate that MIL-102 is stable up to approximately 300 degrees C and shows zeolitic behavior and a hydrogen storage capacity of approximately 1.0 wt % at 77 K when loaded at 3.5 MPa.

Abstract: A new three-dimensional chromium(III) naphthalene tetracarboxylate, CrIII3O(H2O)2F{C10H4(CO2)4}1.5·6H2O (MIL-102), has been synthesized under hydrothermal conditions from an aqueous mixture of Cr(NO3)3·9H2O, naphthalene-1,4,5,8-tetracarboxylic acid, and HF. Its structure, solved ab initio from X-ray powder diffraction data, is built up from the connection of trimers of trivalent chromium octahedra and tetracarboxylate moieties. This creates a three-dimensional structure with an array of small one-dimensional channels filled with free water molecules, which interact through hydrogen bonds with terminal water molecules and oxygen atoms from the carboxylates. Thermogravimetric analysis and X-ray thermodiffractometry indicate that MIL-102 is stable up to ∼300 °C and shows zeolitic behavior. Due to topological frustration effects, MIL-102 remains paramagnetic down to 5 K. Finally, MIL-102 exhibits a hydrogen storage capacity of ∼1.0 wt % at 77 K when loaded at 3.5 MPa (35 bar). The hydrogen uptake is discussed...