D. Volkmer

MOFs for long-term gas storage: Exploiting kinetic trapping in ZIF-8 for on-demand and stimuli-controlled gas release

K. Heinz, S.M.J. Rogge, A. Kalytta-Mewes, D. Volkmer, H. Bunzen
Inorganic Chemistry Frontiers
10, 16, 4763-4772


In this study, we investigate the potential of metal–organic frameworks (MOFs) for long-term gas storage under ambient conditions. Specifically, we selected a MOF ZIF-8 (with a 0.34 nm large pore aperture), which exhibits a temperature- and pressure-regulated gating effect, and loaded it with sulphur hexafluoride (with a kinetic diameter of 0.55 nm). By optimising the loading conditions, we were able to achieve up to 33 wt% SF6 loading into the pores of ZIF-8. Although MOFs featuring gating effects are known to adsorb gases larger than the pore openings, herein, by applying high pressure (and optionally elevated temperature), kinetic trapping of the gas guest was also achieved. When investigating the gas release under ambient conditions, three MOF samples of different crystal sizes (ca. 45 nm, 1.5 μm and 5 μm) were examined. Remarkably, for the largest crystals, more than 86% of the initially loaded gas remained trapped in the pores even after being exposed to air for 100 days under ambient conditions. Our findings indicate that the extremely slow release of SF6 is due to the high activation energy for the guest diffusion through the narrow pore opening in ZIF-8, which was supported by both ab initio-based computational studies and experimental data including modulated thermogravimetric analysis. On the other hand, we also showed that the gas could be released on-demand by applying an elevated temperature or by exposing the MOF to an acidic environment, which opens possibilities for facile gas micro- and nano-dosing applications.


Synthesis, Structural Characterization, and Catalytic Performance of a Vanadium-Based Metal-Organic Framework (COMOC-3)

Y-Y Liu, K. Leus, M. Grzywa, D. Weinberger, K. Strubbe, H. Vrielinck, R. Van Deun, D. Volkmer, V. Van Speybroeck, P. Van der Voort
European Journal of Inorganic Chemistry
(16) 2819 - 2827


A vanadium 2,6-naphthalenedicarboxylate, VIII(OH)(O2C–C10H6–CO2)·H2O, denoted as COMOC-3as (COMOC = Center for Ordered Materials, Organometallics and Catalysis, Ghent University), has been synthesized under hydrothermal conditions by means of both a solvothermal and a microwave synthesis procedure. The structure shows the topology of an aluminium 2,6-naphthalenedicarboxylate, the so-called MIL-69 (MIL = Materials of the Institute Lavoisier). After calcination at 250 °C in air, the VIII center was oxidized to VIV with the structure of VIVO(O2C–C10H6–CO2) (COMOC-3). The oxidation process was verified by cyclic voltammetry and EPR spectroscopy. The crystallinity was investigated by variable-temperature XRD. The title compound is stable against air and moisture. The catalytic performance of COMOC-3 was examined in the liquid-phase oxidation of cyclohexene. COMOC-3 exhibited similar catalytic performance to MIL-47 [VO(O2C–C6H4–CO2)]. The compound is reusable and maintains its catalytic activity through several runs.

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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