J.F.M. Denayer

Hydrogen Clathrates: Next Generation Hydrogen Storage Materials

A. Gupta, G.V. Baron, P. Perreault, S. Lenaerts, R.-G. Ciocarlan, P. Cool, P. M. Mileo, S.M.J. Rogge, V. Van Speybroeck, G. Watson, P. Van der Voort, M. Houlleberghs, E. Breynaert, J.A. Martens, J.F.M. Denayer

Energy Storage Materials

41, 69-107

2021

Abstract

Extensive research has been carried on the molecular adsorption in high surface area materials such as carbonaceous materials and MOFs as well as atomic bonded hydrogen in metals and alloys. Clathrates stand among the ones to be recently suggested for hydrogen storage. Although, the simulations predict lower capacity than the expected by the DOE norms, the additional benefits of clathrates such as low production and operational cost, fully reversible reaction, environmentally benign nature, low risk of flammability make them one of the most promising materials to be explored in the next decade. The inherent ability to tailor the properties of clathrates using techniques such as addition of promoter molecules, use of porous supports and formation of novel reverse micelles morphology provide immense scope customisation and growth. As rapidly evolving materials, clathrates promise to get as close as possible in the search of “holy grail” of hydrogen storage. This review aims to provide the audience with the background of the current developments in the solid-state hydrogen storage materials, with a special focus on the hydrogen clathrates. The in-depth analysis of the hydrogen clathrates will be provided beginning from their discovery, various additives utilised to enhance their thermodynamic and kinetic properties, challenges in the characterisation of hydrogen in clathrates, theoretical developments to justify the experimental findings and the upscaling opportunities presented by this system. The review will present state of the art in the field and also provide a global picture for the path forward.

Gold Open Access

DOI

http://dx.doi.org/10.1016/j.ensm.2021.05.044

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

2013

Abstract

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.

DOI

http://dx.doi.org/10.1021/jp406835n

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

2013

Abstract

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.

DOI

http://dx.doi.org/10.1021/ic301338a

Synthesis, characterization and sorption properties of NH2-MIL-47

K. Leus, S. Couck, M. Vandichel, G. Vanhaelewyn, Y-Y Liu, G.B. Marin, I. Van Driessche, D. Depla, M. Waroquier, V. Van Speybroeck, J.F.M. Denayer, P. Van der Voort

Physical Chemistry Chemical Physics (PCCP)

14, 15562–15570

2012

Abstract

An amino functionalized vanadium-containing Metal Organic Framework, NH₂-MIL-47 has been synthesized by a hydrothermal reaction in an autoclave. Alternatively, a synthesis route via microwave enhanced irradiation has been optimized to accelerate the synthesis. The NH₂-MIL-47 exhibits the same topology as MIL-47, in which the V center is octahedrally coordinated. After an exchange procedure in DMF the V+III center is oxidized to V+IV, which is confirmed by EPR and XPS measurements. The CO² and CH₄ adsorption properties have been evaluated and compared to MIL-47, showing that both MOFs have an almost similar adsorption capacity and affinity for CO². DFT- based molecular modeling calculations were performed to obtain more insight into the adsorption positions for CO² in NH₂-MIL-47. Furthermore our calculated adsorption enthalpies agree well with the experimental values.

DOI

http://dx.doi.org/10.1039/C2CP42137B

Catalytic and molecular separation properties of Zeogrids and Zeotiles

J.A. Martens, J.W. Thybaut, J.F.M. Denayer, S. Pulinthanathu Sree, A. Aerts, M-F. Reyniers, V. Van Speybroeck, M. Waroquier, A. Buekenhoudt, I. Vankelecom, W. Buijs, J. Persoons, G.V. Baron, S. Bals, G. Van Tendeloo, G.B. Marin, P.A. Jacobs, C. Kirschhock

Catalysis Today

168, 17-27

2011

Abstract

Zeogrids and Zeotiles are hierarchical materials built from assembled MFI zeolite precursor units. Permanent secondary porosity in these materials is obtained through self assembly of nanoparticles encountered in MFI zeolite synthesis in the presence of supramolecular templates. Hereon, the aggregated species are termed nanoslabs. Zeogrids are layered materials with lateral spacings between nanoslabs creating galleries qualifying as supermicropores. Zeotiles present a diversity of tridimensional nanoslab assemblies with mesopores. Zeotile-1, -4 and -6 are hexagonal mesostructures. Zeotile-1 has triangular and hexagonal channels; Zeotile-4 has hexagonal channels interconnected via slits. Zeotile-2 has a cubic structure with gyroid type mesoporosity. The behavior of Zeogrids and Zeotiles in adsorption, membrane and chromatographic separation and catalysis has been characterized and compared with zeolites and mesoporous materials derived from unstructured silica sources. Shape selectivity was detected via adsorption of n- and iso-alkanes. The mesoporosity of Zeotiles can be exploited in chromatographic separation of biomolecules. Zeotiles present attractive separation properties relevant to CO2 sequestration. Because of its facile synthesis procedure without hydrothermal steps Zeogrid is convenient for membrane synthesis. The performance of Zeogrid membrane in gas separation, nanofiltration and pervaporation is reported. In the Beckmann rearrangement of cyclohexanone oxime Zeogrids and Zeotiles display a catalytic activity characteristic of silicalite-1 zeolites. Introduction of acidity and redox catalytic activity can be achieved via incorporation of Al and Ti atoms in the nanoslabs during synthesis. Zeogrids are active in hydrocracking, catalytic cracking, alkylation and epoxidation reactions. Zeogrids and Zeotiles often behave differently from ordered mesoporous materials as well as from zeolites and present a valuable extension of the family of hierarchical silicate based materials.