Metal–organic frameworks as catalysts: the role of metal active sites

Valvekens, Pieterjan; Vermoortele, Frederik; Vos, Dirk De

doi:10.1039/c3cy20813c

Cited by 284 publications

(204 citation statements)

References 88 publications

Supporting

Mentioning

191

Contrasting

Order By: Relevance

“…S24-S26) and the observed kinetic parameters are summarized in Tab. 4. These values numerically confirm that the reaction is clearly accelerated at higher temperatures.…”

Section: In-situ Pxrd Studiessupporting

confidence: 76%

“…MOFs exhibiting permanent porosity were shown to be suitable candidates for this approach named isoreticular synthesis. 2 Thus the porosity and surface properties can be easily tuned to yield materials with remarkable performance in fields of application like adsorption, 3 catalysis, 4 luminescence 5 or energy storage. 6 Furthermore, MOFs sometimes show remarkable properties which are rarely paralleled by other crystalline materials.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Combined in- and ex situ studies of pyrazine adsorption into the aliphatic MOF Al-CAU-13: structures, dynamics and correlations

et al. 2017

View full text Add to dashboard Cite

The intercalation of different pyrazines (pyrazine, methylpyrazine, 2,5-dimethylpyrazine, 2,3-dimethylpyrazine, trimethylpyrazine and tetramethylpyrazine) into the trans-1,4-cyclohexanedicarboxylate (CDC 2-) based Al-MOF [Al(OH)(CDC)], denoted as CAU-13, was investigated. The adsorption of the guest molecules into the flexible MOF was carried out from aqueous solution or via vapour phase adsorption, starting with the hydrated narrow-pore form of the framework [Al(OH)(O2C-C6H10-CO2)]·H2O (CAU-13-np). The obtained host-guest systems were characterised by thermogravimetry and vibrational spectroscopy and their crystal structures were elucidated using powder X-ray diffraction (PXRD) data. The crystal structures indicate that guest molecules forming hydrogen-bonds with the host framework (pyrazine, methylpyrazine and 2,5-dimethylpyrazine) induce a slight opening of the channels, resulting in a semi-open framework conformation (CAU-13-so). For the bulkier guests 2,3-dimethylpyrazine, trimethylpyrazine and tetramethylpyrazine, only Van der Waals contacts can be observed between the host and the guest molecules and the large pore conformation is observed (CAU-13-lp). We carried out in-situ PXRD studies using synchrotron radiation during the adsorption of the respective guest molecules from aqueous solutions with various concentrations and at different temperatures. In general, stronger host-guest interactions required milder adsorption conditions while harsher conditions nevertheless accelerated the conversion. The kinetic parameters for the intercalation of pyrazine indicate that the rate limiting step differs, depending on the intercalation temperature.

show abstract

“…S24-S26) and the observed kinetic parameters are summarized in Tab. 4. These values numerically confirm that the reaction is clearly accelerated at higher temperatures.…”

Section: In-situ Pxrd Studiessupporting

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Combined in- and ex situ studies of pyrazine adsorption into the aliphatic MOF Al-CAU-13: structures, dynamics and correlations

et al. 2017

View full text Add to dashboard Cite

show abstract

“…It has been frequently observed that, in order to be used as catalyst, MOFs have to be submitted to an activation process to remove co-adsorbed water and solvent molecules and to generate coordinatively unsaturated sites around the metal centers. 13,22,49,50 In the present case, MIL-101 solids were activated at 150 ○ C under vacuum for 6 h and the performance of the materials submitted to activation compared with that of untreated materials. In all cases it was observed that the only reaction product was the corresponding DBT sulfone (DBTsulfone) and the process is accompanied by some oxidation of the solvent (~ 1 %).…”

Section: Resultsmentioning

confidence: 99%

MIL-101 promotes the efficient aerobic oxidative desulfurization of dibenzothiophenes

et al. 2016

View full text Add to dashboard Cite

MIL-101 promotes the aerobic oxidation in n-dodecane of dibenzothiophene (DBT) and its methyl-substituted derivatives to their corresponding sulfone with complete selectivity, without observation of the sulfoxide. DBT sulfones can be completely separated from n-dodecane by water extraction. MIL-101(Cr) without the need of pre-activation was found more convenient than the also-active MIL-101(Fe) analog. The reaction exhibits an induction period due to the diffusion inside the pore system of the solvent or oxygen and it is not observed if the MIL-101 sample is first contacted with the solvent at the reaction temperature for sufficiently long times. MIL-101 is reusable for at least five times without any sign of deactivation according to the time-conversion plots. Evidence by electron paramagnetic resonance spectroscopy detecting the hydroperoxide radical adduct with a spin trapping agent and Raman spectroscopy detection of superoxide supports that the process is an autooxidation reaction initiated by MIL-101 following the expected radical chain mechanism inside the MIL-101 cages.

show abstract

“…A myriad of applications have been investigated so far, in domains like gas storage, separations and catalysis. [1][2][3] The exploration of the catalytic potential of MOFs however has mainly focused on acid or redox catalysis. Reports on the catalytic activity of MOFs in basecatalyzed reactions are much more scarce, and the reported materials can be divided into two groups.…”

Section: Introductionmentioning

confidence: 99%

Metal-dioxidoterephthalate MOFs of the MOF-74 type: Microporous basic catalysts with well-defined active sites

Valvekens

Vandichel

Waroquier

et al. 2014

Journal of Catalysis

Self Cite

142

122

View full text Add to dashboard Cite

The hybrid frameworks M 2 dobdc (dobdc 4-= 2,5-dioxidoterephthalate, M 2+ = Mg 2+ , Co 2+ , Ni 2+ , Cu 2+ and Zn 2+ ), commonly known as CPO-27 or MOF-74, are shown to be active catalysts in base-catalyzed reactions such as Knoevenagel condensations or Michael additions. Rather than utilizing Nfunctionalized linkers as a source of basicity, the intrinsic basicity of these materials arises from the presence of the phenolate oxygen atoms coordinated to the metal ions. The overall activity is due a complex interplay of the basic properties of these structural phenolates and the reactant binding characteristics of the coordinatively unsaturated sites. The nature of the active site and the order of activity among the different M 2 dobdc materials were rationalized via computational efforts; the most active material, both in theory and experiment, is the Ni-containing variant. The basicity of Ni 2 dobdc was experimentally proven by chemisorption of pyrrole and observation by IR spectroscopy.

show abstract

Metal–organic frameworks as catalysts: the role of metal active sites

Cited by 284 publications

References 88 publications

Combined in- and ex situ studies of pyrazine adsorption into the aliphatic MOF Al-CAU-13: structures, dynamics and correlations

Combined in- and ex situ studies of pyrazine adsorption into the aliphatic MOF Al-CAU-13: structures, dynamics and correlations

MIL-101 promotes the efficient aerobic oxidative desulfurization of dibenzothiophenes

Metal-dioxidoterephthalate MOFs of the MOF-74 type: Microporous basic catalysts with well-defined active sites

Contact Info

Product

Resources

About