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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.

No MeSH data available.


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Oxidation of benzyl alcohol using Cu3(BTC)2 with oxygen.(a) Time conversion plot for the aerobic oxidation of benzyl alcohol to benzaldehyde catalyzed by the Cu3(BTC)2 synthesized in CO2-expanded DMF at 2.0 MPa (green curve), 4.5 MPa (blue curve), 6.6 MPa (red curve) and in pure DMF (black curve). Reaction conditions: benzyl alcohol 0.185 mmol, catalyst 30 mg, DMF 1 ml, TEMPO (0.5 equiv), Na2CO3 (1 equiv), 75 °C, oxygen atmosphere. (b) The reusability of the Cu3(BTC)2 synthesized in CO2-expanded DMF at 6.6 MPa.
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f5: Oxidation of benzyl alcohol using Cu3(BTC)2 with oxygen.(a) Time conversion plot for the aerobic oxidation of benzyl alcohol to benzaldehyde catalyzed by the Cu3(BTC)2 synthesized in CO2-expanded DMF at 2.0 MPa (green curve), 4.5 MPa (blue curve), 6.6 MPa (red curve) and in pure DMF (black curve). Reaction conditions: benzyl alcohol 0.185 mmol, catalyst 30 mg, DMF 1 ml, TEMPO (0.5 equiv), Na2CO3 (1 equiv), 75 °C, oxygen atmosphere. (b) The reusability of the Cu3(BTC)2 synthesized in CO2-expanded DMF at 6.6 MPa.

Mentions: The Cu3(BTC)2 MOFs synthesized in CO2-expanded DMF were used to catalyse the oxidation of benzyl alcohol to benzaldehyde, using 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) as a co-catalyst47. The selectivity of benzaldehyde was >99%. As shown in Fig. 5a, the Cu3(BTC)2 synthesized at higher pressure is more active. By using the Cu3(BTC)2 synthesized at 6.6 MPa, benzyl alcohol converted completely to benzaldehyde at 3 h (red curve). The activities of the three MOFs are higher than that synthesized in pure DMF (black curve), further much higher than that of commercial Cu3(BTC)2 at the same experimental conditions (10% conversion at 3 h)47. The catalyst shows no evident drop in catalytic activity after four runs (Fig. 5b), indicative of the high stability of the MOF. No notable difference was observed for the XRD patterns and SEM images of the fresh Cu3(BTC)2 and that after being reused for four runs (Supplementary Figs 12 and 13), indicating that the structural integrity of the MOF was well preserved. The porosity properties of the Cu3(BTC)2 after being reused for four runs were determined by N2 adsorption–desorption method (Supplementary Fig. 14). The BET surface area of the recycled sample is 685 m2 g−1, which is slightly lower than that of the original sample (728 m2 g−1). The mesopore size distribution of the recycled sample is nearly identical with that of the original one. This indicates that the mesoporous structure of the MOF can be well preserved after being reused for four runs. The slight drop of the BET surface area of the recycled MOF may be due to the presence of some inorganic and organic impurities generated during the reaction that blocks the micropore system47.


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)

Oxidation of benzyl alcohol using Cu3(BTC)2 with oxygen.(a) Time conversion plot for the aerobic oxidation of benzyl alcohol to benzaldehyde catalyzed by the Cu3(BTC)2 synthesized in CO2-expanded DMF at 2.0 MPa (green curve), 4.5 MPa (blue curve), 6.6 MPa (red curve) and in pure DMF (black curve). Reaction conditions: benzyl alcohol 0.185 mmol, catalyst 30 mg, DMF 1 ml, TEMPO (0.5 equiv), Na2CO3 (1 equiv), 75 °C, oxygen atmosphere. (b) The reusability of the Cu3(BTC)2 synthesized in CO2-expanded DMF at 6.6 MPa.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4109014&req=5

f5: Oxidation of benzyl alcohol using Cu3(BTC)2 with oxygen.(a) Time conversion plot for the aerobic oxidation of benzyl alcohol to benzaldehyde catalyzed by the Cu3(BTC)2 synthesized in CO2-expanded DMF at 2.0 MPa (green curve), 4.5 MPa (blue curve), 6.6 MPa (red curve) and in pure DMF (black curve). Reaction conditions: benzyl alcohol 0.185 mmol, catalyst 30 mg, DMF 1 ml, TEMPO (0.5 equiv), Na2CO3 (1 equiv), 75 °C, oxygen atmosphere. (b) The reusability of the Cu3(BTC)2 synthesized in CO2-expanded DMF at 6.6 MPa.
Mentions: The Cu3(BTC)2 MOFs synthesized in CO2-expanded DMF were used to catalyse the oxidation of benzyl alcohol to benzaldehyde, using 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) as a co-catalyst47. The selectivity of benzaldehyde was >99%. As shown in Fig. 5a, the Cu3(BTC)2 synthesized at higher pressure is more active. By using the Cu3(BTC)2 synthesized at 6.6 MPa, benzyl alcohol converted completely to benzaldehyde at 3 h (red curve). The activities of the three MOFs are higher than that synthesized in pure DMF (black curve), further much higher than that of commercial Cu3(BTC)2 at the same experimental conditions (10% conversion at 3 h)47. The catalyst shows no evident drop in catalytic activity after four runs (Fig. 5b), indicative of the high stability of the MOF. No notable difference was observed for the XRD patterns and SEM images of the fresh Cu3(BTC)2 and that after being reused for four runs (Supplementary Figs 12 and 13), indicating that the structural integrity of the MOF was well preserved. The porosity properties of the Cu3(BTC)2 after being reused for four runs were determined by N2 adsorption–desorption method (Supplementary Fig. 14). The BET surface area of the recycled sample is 685 m2 g−1, which is slightly lower than that of the original sample (728 m2 g−1). The mesopore size distribution of the recycled sample is nearly identical with that of the original one. This indicates that the mesoporous structure of the MOF can be well preserved after being reused for four runs. The slight drop of the BET surface area of the recycled MOF may be due to the presence of some inorganic and organic impurities generated during the reaction that blocks the micropore system47.

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