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Highly mesoporous metal-organic framework assembled in a switchable solvent.

Peng L, Zhang J, Xue Z, Han B, Sang X, Liu C, Yang G - Nat Commun (2014)

Bottom Line: The preparation of mesoporous metal-organic frameworks usually needs the supramolecular or cooperative template strategy.Moreover, the use of CO2 can accelerate the reaction for metal-organic framework formation from metal salt and organic linker due to the viscosity-lowering effect of CO2, and the product can be recovered through CO2 extraction.The as-synthesized mesocellular metal-organic frameworks are highly active in catalysing the aerobic oxidation of benzylic alcohols under mild temperature at atmospheric pressure.

View Article: PubMed Central - PubMed

Affiliation: Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.

ABSTRACT
The mesoporous metal-organic frameworks are a family of materials that have pore sizes ranging from 2 to 50 nm, which have shown promising applications in catalysis, adsorption, chemical sensing and so on. The preparation of mesoporous metal-organic frameworks usually needs the supramolecular or cooperative template strategy. Here we report the template-free assembly of mesoporous metal-organic frameworks by using CO2-expanded liquids as switchable solvents. The mesocellular metal-organic frameworks with large mesopores (13-23 nm) are formed, and their porosity properties can be easily adjusted by controlling CO2 pressure. Moreover, the use of CO2 can accelerate the reaction for metal-organic framework formation from metal salt and organic linker due to the viscosity-lowering effect of CO2, and the product can be recovered through CO2 extraction. The as-synthesized mesocellular metal-organic frameworks are highly active in catalysing the aerobic oxidation of benzylic alcohols under mild temperature at atmospheric pressure.

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Porosity measurements.Porosity properties of Cu3(BTC)2 determined by N2 adsorption–desorption method. (a) N2 adsorption–desorption isotherms of the Cu3(BTC)2 synthesized in CO2-expanded DMF at 2.0 MPa (blue curves), 4.5 MPa (red curves) and 6.6 MPa (green curves). (b) The mesopore size distribution curves for the Cu3(BTC)2 synthesized under the same conditions.
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f3: Porosity measurements.Porosity properties of Cu3(BTC)2 determined by N2 adsorption–desorption method. (a) N2 adsorption–desorption isotherms of the Cu3(BTC)2 synthesized in CO2-expanded DMF at 2.0 MPa (blue curves), 4.5 MPa (red curves) and 6.6 MPa (green curves). (b) The mesopore size distribution curves for the Cu3(BTC)2 synthesized under the same conditions.

Mentions: The porosity properties of the Cu3(BTC)2 were determined by N2 adsorption–desorption method after the sample was dried and degassed at 100 °C. Figure 3a shows the N2 adsorption–desorption isotherms of the Cu3(BTC)2 synthesized in CO2-expanded DMF at different pressures. They exhibit an intermediate mode between type I and type IV, which are related to mesoporous and microporous materials, respectively. The mesopore size distribution curves, calculated from Barrett–Joyner–Halenda analysis, are shown in Fig. 3b. The mesopore diameters of the Cu3(BTC)2 synthesized at 2.0, 4.5 and 6.6 MPa are centred at 13, 20 and 23 nm, respectively. Evidently, higher CO2 pressure favours the formation of larger mesopores, which is consistent with the scanning electron microscopic (SEM) observations. From N2 adsorption–desorption isotherm, the diameter of the micropores was calculated to be 0.85 nm by Horvath–Kawazoe analysis (Supplementary Fig. 6), in agreement with the micropore diameter estimated from crystallographic data of Cu3(BTC)2 (ref. 37). The porosity properties of the MOFs were further characterized by small-angle X-ray scattering (SAXS) and the results are shown in Supplementary Fig. 7. The SAXS profiles (Supplementary Fig. 7A) display power law scattering of Q−4 in the low Q region (Q<0.08 Å−1), corresponding to the asymptotic scattering behaviour of mesopores43. The mesopore size distributions of the MOFs synthesized at pressure of 2.0, 4.5 and 6.6 MPa were calculated, which are centred at about 13.8, 19.0 and 21.1 nm (Supplementary Fig. 7B). These results are consistent with the mesopore size distributions obtained from N2 adsorption–desorption. The results prove the formation of hierarchically meso- and microporous MOFs in CXL and the mesopore size can be easily tuned by varying pressure.


Highly mesoporous metal-organic framework assembled in a switchable solvent.

Peng L, Zhang J, Xue Z, Han B, Sang X, Liu C, Yang G - Nat Commun (2014)

Porosity measurements.Porosity properties of Cu3(BTC)2 determined by N2 adsorption–desorption method. (a) N2 adsorption–desorption isotherms of the Cu3(BTC)2 synthesized in CO2-expanded DMF at 2.0 MPa (blue curves), 4.5 MPa (red curves) and 6.6 MPa (green curves). (b) The mesopore size distribution curves for the Cu3(BTC)2 synthesized under the same conditions.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4109014&req=5

f3: Porosity measurements.Porosity properties of Cu3(BTC)2 determined by N2 adsorption–desorption method. (a) N2 adsorption–desorption isotherms of the Cu3(BTC)2 synthesized in CO2-expanded DMF at 2.0 MPa (blue curves), 4.5 MPa (red curves) and 6.6 MPa (green curves). (b) The mesopore size distribution curves for the Cu3(BTC)2 synthesized under the same conditions.
Mentions: The porosity properties of the Cu3(BTC)2 were determined by N2 adsorption–desorption method after the sample was dried and degassed at 100 °C. Figure 3a shows the N2 adsorption–desorption isotherms of the Cu3(BTC)2 synthesized in CO2-expanded DMF at different pressures. They exhibit an intermediate mode between type I and type IV, which are related to mesoporous and microporous materials, respectively. The mesopore size distribution curves, calculated from Barrett–Joyner–Halenda analysis, are shown in Fig. 3b. The mesopore diameters of the Cu3(BTC)2 synthesized at 2.0, 4.5 and 6.6 MPa are centred at 13, 20 and 23 nm, respectively. Evidently, higher CO2 pressure favours the formation of larger mesopores, which is consistent with the scanning electron microscopic (SEM) observations. From N2 adsorption–desorption isotherm, the diameter of the micropores was calculated to be 0.85 nm by Horvath–Kawazoe analysis (Supplementary Fig. 6), in agreement with the micropore diameter estimated from crystallographic data of Cu3(BTC)2 (ref. 37). The porosity properties of the MOFs were further characterized by small-angle X-ray scattering (SAXS) and the results are shown in Supplementary Fig. 7. The SAXS profiles (Supplementary Fig. 7A) display power law scattering of Q−4 in the low Q region (Q<0.08 Å−1), corresponding to the asymptotic scattering behaviour of mesopores43. The mesopore size distributions of the MOFs synthesized at pressure of 2.0, 4.5 and 6.6 MPa were calculated, which are centred at about 13.8, 19.0 and 21.1 nm (Supplementary Fig. 7B). These results are consistent with the mesopore size distributions obtained from N2 adsorption–desorption. The results prove the formation of hierarchically meso- and microporous MOFs in CXL and the mesopore size can be easily tuned by varying pressure.

Bottom Line: The preparation of mesoporous metal-organic frameworks usually needs the supramolecular or cooperative template strategy.Moreover, the use of CO2 can accelerate the reaction for metal-organic framework formation from metal salt and organic linker due to the viscosity-lowering effect of CO2, and the product can be recovered through CO2 extraction.The as-synthesized mesocellular metal-organic frameworks are highly active in catalysing the aerobic oxidation of benzylic alcohols under mild temperature at atmospheric pressure.

View Article: PubMed Central - PubMed

Affiliation: Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.

ABSTRACT
The mesoporous metal-organic frameworks are a family of materials that have pore sizes ranging from 2 to 50 nm, which have shown promising applications in catalysis, adsorption, chemical sensing and so on. The preparation of mesoporous metal-organic frameworks usually needs the supramolecular or cooperative template strategy. Here we report the template-free assembly of mesoporous metal-organic frameworks by using CO2-expanded liquids as switchable solvents. The mesocellular metal-organic frameworks with large mesopores (13-23 nm) are formed, and their porosity properties can be easily adjusted by controlling CO2 pressure. Moreover, the use of CO2 can accelerate the reaction for metal-organic framework formation from metal salt and organic linker due to the viscosity-lowering effect of CO2, and the product can be recovered through CO2 extraction. The as-synthesized mesocellular metal-organic frameworks are highly active in catalysing the aerobic oxidation of benzylic alcohols under mild temperature at atmospheric pressure.

No MeSH data available.


Related in: MedlinePlus