Synthesis, characterization and sorption properties of functionalized Cr-MIL-101-X (X=-F, -Cl, -Br, -CH3, -C6H4, -F2, -(CH3)2) materials

Four existing and three new functionalized chromium terephthalates having MIL-101 topology and denoted as Cr-MIL-101-X (existing ones with X=-F, 1-F; -Cl, 2-Cl; -Br, 3-Br; -CH3, 4-CH3; new ones with X=-C6H4, 5-C6H4; -F-2, 6-F-2, -(CH3)(2), 7-(CH3)(2)) were synthesized under hydrothermal conditions. All the materials except 5-C6H4 could be prepared by a general synthetic route, in which the mixtures of CrO3, H2BDC-X (BDC=1,4-benzenedicarboxylate) linkers, conc. HCl and water with a molar ratio of 1:1:3.9:222.2 were reacted at 180 degrees C for 144 h. Compared to the 144 h of synthesis time, three of the compounds, namely 1-CI, 2-Br and 5-C6H4, could be prepared in much shorter reaction times (12-18 h at 180-210 degrees C). The materials possess high thermal stability up to 270-300 degrees C in an air atmosphere. The activated compounds exhibit significant porosity (S-BET range: 1273-2135 m(2) g(-1)). At 0 degrees C and 1 bar, the CO2 adsorption capacities of the compounds fall in the 1.7-2.9 mmol g(-1) range. Compounds 1-F and 6-F-2 showed enhanced CO2 uptake values compared to parent Cr-MIL-101. The benzene adsorption capacities of the compounds lie in the range of 66.2-139.5 molecules per unit cell at 50 degrees C and p/P-0=0.35. The increased benzene uptake value of 1-F compared to un-functionalized Cr-MIL-101 and 4-CH3 suggests that the fluorination has induced more hydrophobicity in Cr-MIL-101 as compared to the methylation. (C) 2016 Elsevier Inc. All rights reserved.