Synthesis preparations. MIL-101(Cr) was synthesised by adjusting a previously reported methodology.23a Cr(NO3)3·9H2O (10 mmol) and H2BDC (10 mmol) were added to deionised water (50 mL). The resulting suspension was heated up to 473 K for 8 h, under autogenous pressure, in a Teflon-lined autoclave. After the synthesis was finished the product was recovered by filtration and then washed with DMF (5 mL), to eliminate any unreacted ligand and dried at 313 K for 12 h. Thermogravimetric analysis (thermal stability up to approximately 488 K, see Fig. S1, ESI‡) and bulk powder X-ray diffraction patterns (see Fig. S2, ESI‡) confirmed the purity of the synthesised material. Elemental analysis data corresponded to [Cr3O(BDC)3]Cl(H2O)4.5(DMF)3.5: calcd (%) for MT= 1070 g mol-1: C 38.7; H 4.47; N 4.58; found: C 38.41; H 4.48; N 4.51%. Before the adsorption experiments the samples of MIL-101(Cr) were acetone-exchanged14 to remove any uncoordinated solvents (water and DMF) from the pores. These samples were activated at 453 K for 2 h (with a heating ramp of 5 K min-1) under vacuum (10-3 bar) to afford the fully desolvated MIL-101(Cr) samples. A fully activated sample of MIL-101(Cr) was analysed by elemental analysis data which corresponded to [Cr3O(BDC)3]·Cl: calcd (%) for MT= 700 g mol-1: C 41.19; H 1.73; found: C 41.11; H 1.69%. N2 adsorption isotherms at 77 K (Fig. S3, ESI‡) for such activated MIL-101(Cr) were used to estimate the BET surface area (0.01 < P/P0 < 0.18) of 2916 m2 g-1 and a pore volume of 1.32 cm3 g-1. It is noteworthy that this adjusted synthetic methodology afforded one of the highest surface areas for MIL-101(Cr) when compared to the previously reported HF-free solvothermal