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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.


SEM images of the Cu3(BTC)2 synthesized in CO2-expanded DMF.(a,b) 2.0; (c,d) 4.5; (e,f) 6.6 MPa. Scale bars, 150, 50, 500, 150, 500 and 150 nm for (a–f), respectively.
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f2: SEM images of the Cu3(BTC)2 synthesized in CO2-expanded DMF.(a,b) 2.0; (c,d) 4.5; (e,f) 6.6 MPa. Scale bars, 150, 50, 500, 150, 500 and 150 nm for (a–f), respectively.

Mentions: The Cu3(BTC)2 synthesized in pure DMF (in the absence of CO2) appeared as irregular agglomerates (Supplementary Fig. 1). However, the mesocellular MOFs were formed in the CO2-expanded DMF. The Cu3(BTC)2 synthesized at 2.0 MPa exhibits thick pore walls and mesopores of average size of 10 nm (Fig. 2a,b). When the pressure is increased to 4.5 MPa, the MOF is more porous, with thinner mesopore walls (Fig. 2c,d). The Cu3(BTC)2 synthesized at 6.6 MPa has mesopores in 20–30 nm and the diameters of the pore walls are around 10 nm (Fig. 2e,f). Clearly, higher CO2 pressure is favourable to form more porous MOFs, with larger mesopores and thinner pore walls. The X-ray diffraction (XRD) peak positions and relative intensities of the as-synthesized MOFs agree well with those of the simulated HKUST-1 (ref. 37; Supplementary Fig. 2). Fourier transform infrared spectra (Supplementary Fig. 3) revealed that the carboxylate groups of H3BTC were coordinated to Cu(II) ions91840. The characteristic C=O stretching vibration for acetic acid (1,770–1,750 cm−1) and C–N stretching vibration (1,230–1,030 cm−1) for triethylamine were not observed, indicating that the product is free of acetic acid and triethylamine, which could be removed easily by washing with ethanol. Energy-dispersive X-ray spectrum (Supplementary Fig. 4) demonstrates the presence of copper, oxygen and carbon in the prepared MOF and no N element was detected, further proving the absence of triethylamine in the product. The MOFs could keep stable up to 310 °C, as evidenced by thermogravimetric analysis (Supplementary Fig. 5), comparable to that of bulk HKUST-1 (refs 41, 42).


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)

SEM images of the Cu3(BTC)2 synthesized in CO2-expanded DMF.(a,b) 2.0; (c,d) 4.5; (e,f) 6.6 MPa. Scale bars, 150, 50, 500, 150, 500 and 150 nm for (a–f), respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: SEM images of the Cu3(BTC)2 synthesized in CO2-expanded DMF.(a,b) 2.0; (c,d) 4.5; (e,f) 6.6 MPa. Scale bars, 150, 50, 500, 150, 500 and 150 nm for (a–f), respectively.
Mentions: The Cu3(BTC)2 synthesized in pure DMF (in the absence of CO2) appeared as irregular agglomerates (Supplementary Fig. 1). However, the mesocellular MOFs were formed in the CO2-expanded DMF. The Cu3(BTC)2 synthesized at 2.0 MPa exhibits thick pore walls and mesopores of average size of 10 nm (Fig. 2a,b). When the pressure is increased to 4.5 MPa, the MOF is more porous, with thinner mesopore walls (Fig. 2c,d). The Cu3(BTC)2 synthesized at 6.6 MPa has mesopores in 20–30 nm and the diameters of the pore walls are around 10 nm (Fig. 2e,f). Clearly, higher CO2 pressure is favourable to form more porous MOFs, with larger mesopores and thinner pore walls. The X-ray diffraction (XRD) peak positions and relative intensities of the as-synthesized MOFs agree well with those of the simulated HKUST-1 (ref. 37; Supplementary Fig. 2). Fourier transform infrared spectra (Supplementary Fig. 3) revealed that the carboxylate groups of H3BTC were coordinated to Cu(II) ions91840. The characteristic C=O stretching vibration for acetic acid (1,770–1,750 cm−1) and C–N stretching vibration (1,230–1,030 cm−1) for triethylamine were not observed, indicating that the product is free of acetic acid and triethylamine, which could be removed easily by washing with ethanol. Energy-dispersive X-ray spectrum (Supplementary Fig. 4) demonstrates the presence of copper, oxygen and carbon in the prepared MOF and no N element was detected, further proving the absence of triethylamine in the product. The MOFs could keep stable up to 310 °C, as evidenced by thermogravimetric analysis (Supplementary Fig. 5), comparable to that of bulk HKUST-1 (refs 41, 42).

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.