Solvent effect on the synthesis of MIL-96(Cr) and MIL-100(Cr)

In this study, the impact of different solvents on structure formation in the Cr/H3BTC system has been investigated. A new chromium trimesate, designated as MIL-96(Cr), has been synthesized under solvo-thermal conditions in the presence of 1,3,5-benzenetricarboxylic acid (trimesic acid or H3BTC) in a mixed solvent of H2O and CH3OH. This synthesis differs from the hydrothermal preparation of the other three analogues of the MIL-96 structural type (MIL-96(AI). MIL-96(Ga), and MIL-96(In)). MIL-96(Cr) represents another phase resulting from the coordination of Cr3+ and H3BTC besides MIL-100(Cr). These two materials show similar thermal behavior. Gas desorption isotherms have shown that MIL-96(Cr) exhibits a hydrogen storage capacity of up to 8.55 mmol g(-1) at 77 K under 2 MPa and is able to absorb methane up to 3.84 mmol g(-1) at 273 K and 3.23 mmol g(-1) at 303 K under 2 MPa, while MIL-100(Cr) showed more promising results: 14 mmol g(-1) hydrogen at 77K and 1.8 MPa, 4.54 mmol g(-1) methane at 273 K and 2 MPa, and 3.49 mmol g(-1) methane at 303 K and 2 M Pa. (C) 2011 Elsevier Inc. All rights reserved.