A general strategy for the synthesis of functionalised UiO-66 frameworks : characterisation, stability and CO₂ adsorption properties

A general synthetic strategy has been developed, which can be used for the preparation of all the known as well as five new functionalised UiO-66-X compounds [X = H, F, F-2, Cl, Cl-2, Br, Br-2, I, CH3, (CH3)(2), CF3, (CF3)(2), NO2, NH2, OH, (OH)(2), OCH3, (CO2H)(2), SO3H, C6H4]. Starting from a reaction mixture of ZrOCl2 center dot 8H(2)O, H2BDC-X (BDC: 1,4-benzenedicarboxylate), formic acid and N,N-dimethylacetamide (DMA) having a molar ratio of 1:1:100:104.44, all the UiO-66-X compounds, except UiO-66-CO2H, were obtained under solvothermal conditions (150 degrees C, 24 h). The phase purity of all the compounds was ascertained by X-ray powder diffraction (XRPD) analysis, DRIFT spectroscopy and elemental analysis. Determination of lattice parameters from the XRPD patterns of the new thermally activated UiO-66-X {X = CF3 (1-CF3), (CO2H)(2) [2-(CO2H)(2)], F-2 (3-F-2), Cl-2 (4-Cl-2), Br-2 (5-Br-2)} compounds revealed their structural similarity with the unfunctionalised UiO-66. Thermogravimetric analyses (TGA) indicate that the five new compounds are stable in the range 290-390 degrees C in air. Except for 3-F-2, the new compounds maintain their structural integrity in water, acetic acid and 1 M HCl, as verified by XRPD analysis of the samples recovered after suspending them in the respective liquids. As confirmed by N-2 and CO2 sorption analyses, all of the new thermally activated compounds exhibit significant microporosity values (S-Langmuir = 217-836 m(2)g(-1)), which are lower than that of the parent UiO-66. Comparative CO2 sorption studies reveal that the UiO-66-X compounds with X = NO2, NH2, OH, CH3 and (CH3)(2) show enhanced CO2 uptake compared to that of the parent compound at 1 bar and 0 degrees C

Comparison of different solid adsorbents for the removal of mobile pesticides from aqueous solutions

The intensive use of mobile plant protection products, such as bentazon, clopyralid and isoproturon, in agriculture has led to an increasing contamination of groundwater and surface water. In this study, the sorption capacity of various activated carbon samples, metal-organic frameworks (MOFs) and resins were compared. After an initial screening the activated carbon samples and the activated carbon related resin Lewatit AF 5 were selected to characterize the total sorption dynamics. Based on the Freundlich isotherms, the zeolites and MOFs performed well because of their more rapid adsorption of a large amount of pesticides and the lower affinity for the pesticides in view of regeneration. On the other hand, the Temkin model showed physisorption for all adsorbents. Finally, the unstable structure of MOF-235, of which -ions were split off when it comes into contact with a liquid, excluded regeneration of this material

Vanadium analogues of nonfunctionalized and amino-functionalized MOFs with MIL-101 topology : synthesis, characterization, and gas sorption properties

Syntheses, characterization, and gas sorption properties of two new vanadium-based metalorganic frameworks [V3OCl(DMF)2(BDC)3].3.1DMF.10H2O.0.1BDC (VMIL-101 or 1) and [V3OCl(DMF)2(BDCNH2)3].2.8DMF.H2O.0.1BDCNH2 (VMIL-101NH2 or 2) (DMF = N,N'-dimethylformamide; BDC = terephthalate; BDCNH2 = 2-aminoterephthalate) having MIL-101 topology are presented. Compounds 1 and 2 were prepared under similar solvothermal conditions (150 degrees C, 24 h) in DMF by using VCl3 and H2BDC or H2BDCNH2, respectively. Determination of lattice parameters from X-ray powder diffraction (XRPD) patterns of thermally activated compounds revealed their structural similarity with chromium-, iron-, and aluminum-based solids having two types of mesoporous cages and accessible metal sites. The phase purity of the compounds was ascertained by XRPD analysis, diffuse reflectance Fourier transform (DRIFT) spectroscopy, and elemental analysis. Thermogravimetric analyses (TGA) and temperature-dependent XRPD (TDXRPD) experiments indicate that the compounds are stable up to 320 and 240 degrees C, respectively, under an argon atmosphere. Removal of the guest DMF molecules by thermal activation enables the compounds to adsorb significant amounts of N2 (690 and 555 cm3/g at p/p0 = 1 for 1 and 2, respectively) and CO2 (9.0 and 4.3 mmol/g at 24.5 and 22.8 bar for 1 and 2, respectively)

Dioxygen activation in photooxidation of diphenylmethane by a dioxomolybdenum(VI) complex anchored covalently onto mesoporous titania

A dioxomolybdenum(VI) complex has been covalently anchored onto mesoporous titania by a silicon-assisted transesterification route. The grafting of the complex to the mesoporous structure was confirmed by diffuse reflectance infrared Fourier transform, Raman and UV-Vis spectroscopy and by nitrogen sorption experiments. The ability of the grafted complex to activate molecular oxygen (O-2) has been evaluated in the photooxidation of diphenylmethane to produce benzophenone. The photooxidation of diphenylmethane was monitored continuously by in situ dispersive Raman spectroscopy. A scheme for the activation of molecular oxygen under very mild conditions is proposed. A comparison with the same complex anchored onto commercial titanium P-25 and silica gel revealed both the beneficial effect of the mesoporous structure and the existence of a synergistic effect between MoO/TiO2/O-2/light entities, which promotes the photooxidation process under green chemistry conditions. Finally, the heterogeneous catalyst is sustainable; it can be recycled and reused without significant loss in activity or selectivity