S. Biswas

Vanadium Metal-Organic Frameworks: Structures and Applications

P. Van der Voort, K. Leus, Y-Y Liu, M. Vandichel, V. Van Speybroeck, M. Waroquier, S. Biswas
New Journal of Chemistry
38, 1853-1867


This perspective review paper describes the V-containing Metal-Organic Framworks that have been developed since the first systematic reports on MOFs almost 15 years ago. These hybrid crystalline materials, containing V(III) or V(IV) as metal nodes show interesting behaviour in oxidation catalysis and gas sorption. A significant amount of papers has appeared on the use of these structures in gas (hydrocarbon, CO2) separation. Promising future research and development of V-MOFs is suggested.

Open Access version available at UGent repository

New Functionalized Metal–Organic Frameworks MIL-47-X (X = −Cl, −Br, −CH3, −CF3, −OH, −OCH3): Synthesis, Characterization, and CO2 Adsorption Properties

S. Biswas, D.E.P. Vanpoucke, T. Verstraelen, M. Vandichel, S. Couck, K. Leus, Y-Y Liu, M. Waroquier, V. Van Speybroeck, J.F.M. Denayer, P. Van der Voort
Journal of Physical Chemistry C
117 (44), 22784–22796


Six new functionalized vanadium hydroxo terephthalates [VIII(OH)(BDC-X)]•n(guests) (MIL-47(VIII)-X-AS) (BDC = 1,4-benzenedicarboxylate; X = -Cl; -Br, -CH3, -CF3, -OH, -OCH3; AS = as-synthesized) along with the parent MIL-47 were synthesized under rapid microwave-assisted hydrothermal conditions (170 ºC, 30 min, 150 W). The unreacted H2BDC-X and/or occluded solvent molecules can be removed by thermal activation under vacuum leading to the empty-pore forms of the title compounds (MIL-47(VIV)-X). Except pristine MIL-47 (+III oxidation state), the vanadium atoms in all the evacuated functionalized solids stayed in +IV oxidation state. The phase purity of the compounds was ascertained by X-ray powder diffraction (XRPD), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, Raman, thermogravimetric (TG), and elemental analysis. The structural similarity of the filled and empty-pore forms of the functionalized compounds with the respective forms of parent MIL-47 was verified by cell parameter determination from XRPD data. TGA and temperature-dependent XRPD (TDXRPD) experiments in air atmosphere indicate high thermal stability in the range 330-385 ºC. All the thermally activated compounds exhibit significant microporosity (SLangmuir in the range 418-1104 m2 g-1), as verified by the N2 and CO2 sorption analysis. Among the six functionalized compounds, MIL-47(VIV)-OCH3 shows the highest CO2 uptake, demonstrating the determining role of functional groups on the CO2 sorption behaviour. For this compound and pristine MIL-47(VIV), Widom particle insertion simulations were performed based on ab initio calculated crystal structures. The theoretical Henry coefficients show a good agreement with the experimental values, and calculated isosurfaces for the local excess chemical potential indicate the enhanced CO2 affinity is due to two effects: (i) the interaction between the methoxy group and CO2 and (ii) the collapse of the MIL-47(VIV)-OCH3 framework.

Catalytic Performance of Vanadium MIL-47 and Linker-Substituted Variants in the Oxidation of Cyclohexene: A Combined Theoretical and Experimental Approach

M. Vandichel, S. Biswas, K. Leus, J. Paier, J. Sauer, T. Verstraelen, P. Van der Voort, M. Waroquier, V. Van Speybroeck
79 (8), 1183–1197


The epoxidation of cyclohexene has been investigated on a metal–organic framework MIL-47 containing saturated V+IV sites linked with functionalized terephthalate linkers (MIL-47-X, X=OH, F, Cl, Br, CH3, NH2). Experimental catalytic tests have been performed on the MIL-47-X materials to elucidate the effect of linker substitution on the conversion. Notwithstanding the fact that these substituted materials are prone to leaching in the performed catalytic tests, the initial catalytic activity of these materials correlates with the Hammett substituent constants. In general, substituents led to an increased activity relative to the parent MIL-47. To rationalize the experimental findings, first-principles kinetic calculations were performed on periodic models of MIL-47 to determine the most important active sites by creating defect structures in the interior of the crystalline material. In a next step these defect structures were used to propose extended cluster models, which are able to reproduce in an adequate way the direct environment of the active metal site. An alkylperoxo species V+VO(OOtBu) was identified as the most abundant and therefore the most active epoxidation site. The structure of the most active site was a starting basis for the construction of extended cluster models including substituents. They were used for quantifying the effect of functionalization of the linkers on the catalytic performance of the heterogeneous catalyst MIL-47-X. Electron-withdrawing as well as electron-donating groups have been considered. The epoxidation activity of the functionalized models has been compared with the measured experimental conversion of cyclohexene. The agreement is fairly good. This combined experimental–theoretical study makes it possible to elucidate the structure of the most active site and to quantify the electronic modulating effects of linker substituents on the catalytic activity.

New V-IV-Based Metal-Organic Framework Having Framework Flexibility and High CO2 Adsorption Capacity

Y-Y Liu, S. Couck, M. Vandichel, M. Grzywa, K. Leus, S. Biswas, D. Volkmer, J. Gascon, F. Kapteijn, J.F.M. Denayer, M. Waroquier, V. Van Speybroeck, P. Van der Voort
Inorganic Chemistry
52 (1), 113-120


A vanadium based metal–organic framework (MOF), VO(BPDC) (BPDC2– = biphenyl-4,4′-dicarboxylate), adopting an expanded MIL-47 structure type, has been synthesized via solvothermal and microwave methods. Its structural and gas/vapor sorption properties have been studied. This compound displays a distinct breathing effect toward certain adsorptives at workable temperatures. The sorption isotherms of CO2 and CH4 indicate a different sorption behavior at specific temperatures. In situ synchrotron X-ray powder diffraction measurements and molecular simulations have been utilized to characterize the structural transition. The experimental measurements clearly suggest the existence of both narrow pore and large pore forms. A free energy profile along the pore angle was computationally determined for the empty host framework. Apart from a regular large pore and a regular narrow pore form, an overstretched narrow pore form has also been found. Additionally, a variety of spectroscopic techniques combined with N2 adsorption/desorption isotherms measured at 77 K demonstrate that the existence of the mixed oxidation states VIII/VIV in the titled MOF structure compared to pure VIV increases the difficulty in triggering the flexibility of the framework.

A new series of V IV based metal-organic frameworks having framework flexibility and high CO2 adsorption capacity


Conference / event / venue 

Edinburgh UK
Sunday, 16 September, 2012 to Wednesday, 19 September, 2012
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