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A synthetic route to ultralight hierarchically micro/mesoporous Al(III)-carboxylate metal-organic aerogels.

Li L, Xiang S, Cao S, Zhang J, Ouyang G, Chen L, Su CY - Nat Commun (2013)

Bottom Line: Developing a synthetic methodology for the fabrication of hierarchically porous metal-organic monoliths that feature high surface area, low density and tunable porosity is imperative for mass transfer applications, including bulky molecule capture, heterogeneous catalysis and drug delivery.Heating represents a key factor in the control of gelation versus crystallization of Al(III)-multicarboxylate systems.The porosity of the resulting metal-organic aerogels can be readily tuned, leading to the formation of well-ordered intraparticle micropores and aerogel-specific interparticle mesopores, thereby integrating the merits of both crystalline metal-organic frameworks and light aerogels.

View Article: PubMed Central - PubMed

Affiliation: MOE Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, Lehn Institute of Functional Materials, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275, China.

ABSTRACT
Developing a synthetic methodology for the fabrication of hierarchically porous metal-organic monoliths that feature high surface area, low density and tunable porosity is imperative for mass transfer applications, including bulky molecule capture, heterogeneous catalysis and drug delivery. Here we report a versatile and facile synthetic route towards ultralight micro/mesoporous metal-organic aerogels based on the two-step gelation of metal-organic framework nanoparticles. Heating represents a key factor in the control of gelation versus crystallization of Al(III)-multicarboxylate systems. The porosity of the resulting metal-organic aerogels can be readily tuned, leading to the formation of well-ordered intraparticle micropores and aerogel-specific interparticle mesopores, thereby integrating the merits of both crystalline metal-organic frameworks and light aerogels. The hierarchical micro/mesoporosity of the Al-metal-organic aerogels is thoroughly evaluated by N₂ sorption. The good accessibility of the micro/mesopores is verified by vapour/dye uptake, and their potential for utilization as effective fibre-coating absorbents is tested in solid-phase microextraction analyses.

No MeSH data available.


Representative N2 sorption data.(a,b) The N2 adsorption–desorption isotherms of AlBDC-3:2 series MOAs at 77 K (the inserts show enlarged parts of isotherms). (c) The N2 adsorption–desorption isotherms of the templated MOAs at 77 K. (d) The SF micropore distribution of the AlBDC-3:2 series MOAs. (e) The BJH pore distribution of the AlBDC-3:2 series MOAs (vertical offsets). (f) The SF micropore distribution of the templated MOAs. (g) The BJH pore distribution of the templated MOAs.
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f3: Representative N2 sorption data.(a,b) The N2 adsorption–desorption isotherms of AlBDC-3:2 series MOAs at 77 K (the inserts show enlarged parts of isotherms). (c) The N2 adsorption–desorption isotherms of the templated MOAs at 77 K. (d) The SF micropore distribution of the AlBDC-3:2 series MOAs. (e) The BJH pore distribution of the AlBDC-3:2 series MOAs (vertical offsets). (f) The SF micropore distribution of the templated MOAs. (g) The BJH pore distribution of the templated MOAs.

Mentions: To evaluate the porous properties of the Al-MOAs obtained by subcritical CO2(l) extraction of the corresponding Al-MOGs, a series of AlBTC and AlBDC aerogels were subjected to N2 sorption analyses to determine the surface areas, pore volumes and pore sizes (Table 1, Supplementary Tables S9 and S10; Fig. 3, Supplementary Figs S35–S40). The N2 sorption isotherms are between type-I, which is characteristic of microporous materials, and type-IV, which is characteristic of mesoporous materials, showing sheer gas uptake at low pressures and pore condensation with significant adsorption–desorption hysteresis at high pressures. This clearly denotes the coexistence of micro- and mesopores in these Al-MOAs111213. The steep increase in the region of P/P0<0.1 is attributed to micropore filling. For the AlBDC-3:2 series MOAs, the Saito-Foley (SF) micropore sizes are narrowly centred at ~0.9 nm, in agreement with the channel size of the MIL-53(Al) crystal in LP form45, which further confirms that the MOFPs of MIL-53 contribute to the aerogel microporosity. For the AlBTC-1:1 and AlBTC-3:2 series MOAs, the SF micropore sizes are distributed in a wider range centred at ~1.0 nm (Supplementary Figs S35 and S36), indicating that these MOAs might contain mixed MOF phases. The specific surface areas and mesopore parameters of MOAs can be tuned by changing the reactant concentrations, as observed from the distinguishable sorption behaviours, depending on the reactant concentrations (Fig. 3 and Supplementary Figs S35 and S36). For example, when the concentration of the AlBDC-3:2 gel is 0.05 mol l−1, the isotherm shows an H2-type hysteresis loop starting at P/P0=0.43. The mesoporous volume is ~0.76 cm3 g−1, with the mesopores exhibiting a narrow size distribution centred at ~5.4 nm. As the concentration increases to 0.15 mol l−1, the mesoporous volume significantly increases to ~2.25 cm3 g−1, and the pore size becomes larger and wider, centring around ~23.0 nm. The BET surface areas vary up to ~1,324 m2 g−1, in accordance with the contributions of the micro- and mesopore volumes, of which the total pore volume is mainly contributed by the mesopores at higher concentration. This is demonstrated by the fact that the hysteresis loops move and condense into higher pressure region (H1-type). At high concentration of 0.2 mol l−1, the pore sizes show significantly widened distribution at ~87.8 nm, which spans the meso- and macropore sizes. These results are indicative of remarkable influence of concentration on the texture and porosity of MOAs. A similar effect also can be observed for the AlBTC-1:1 and AlBTC-3:2 series (Supplementary Table S9); however, the concentration-pore-size dependency becomes less regular, probably as a result of mixed phases of the MOF particles.


A synthetic route to ultralight hierarchically micro/mesoporous Al(III)-carboxylate metal-organic aerogels.

Li L, Xiang S, Cao S, Zhang J, Ouyang G, Chen L, Su CY - Nat Commun (2013)

Representative N2 sorption data.(a,b) The N2 adsorption–desorption isotherms of AlBDC-3:2 series MOAs at 77 K (the inserts show enlarged parts of isotherms). (c) The N2 adsorption–desorption isotherms of the templated MOAs at 77 K. (d) The SF micropore distribution of the AlBDC-3:2 series MOAs. (e) The BJH pore distribution of the AlBDC-3:2 series MOAs (vertical offsets). (f) The SF micropore distribution of the templated MOAs. (g) The BJH pore distribution of the templated MOAs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3644084&req=5

f3: Representative N2 sorption data.(a,b) The N2 adsorption–desorption isotherms of AlBDC-3:2 series MOAs at 77 K (the inserts show enlarged parts of isotherms). (c) The N2 adsorption–desorption isotherms of the templated MOAs at 77 K. (d) The SF micropore distribution of the AlBDC-3:2 series MOAs. (e) The BJH pore distribution of the AlBDC-3:2 series MOAs (vertical offsets). (f) The SF micropore distribution of the templated MOAs. (g) The BJH pore distribution of the templated MOAs.
Mentions: To evaluate the porous properties of the Al-MOAs obtained by subcritical CO2(l) extraction of the corresponding Al-MOGs, a series of AlBTC and AlBDC aerogels were subjected to N2 sorption analyses to determine the surface areas, pore volumes and pore sizes (Table 1, Supplementary Tables S9 and S10; Fig. 3, Supplementary Figs S35–S40). The N2 sorption isotherms are between type-I, which is characteristic of microporous materials, and type-IV, which is characteristic of mesoporous materials, showing sheer gas uptake at low pressures and pore condensation with significant adsorption–desorption hysteresis at high pressures. This clearly denotes the coexistence of micro- and mesopores in these Al-MOAs111213. The steep increase in the region of P/P0<0.1 is attributed to micropore filling. For the AlBDC-3:2 series MOAs, the Saito-Foley (SF) micropore sizes are narrowly centred at ~0.9 nm, in agreement with the channel size of the MIL-53(Al) crystal in LP form45, which further confirms that the MOFPs of MIL-53 contribute to the aerogel microporosity. For the AlBTC-1:1 and AlBTC-3:2 series MOAs, the SF micropore sizes are distributed in a wider range centred at ~1.0 nm (Supplementary Figs S35 and S36), indicating that these MOAs might contain mixed MOF phases. The specific surface areas and mesopore parameters of MOAs can be tuned by changing the reactant concentrations, as observed from the distinguishable sorption behaviours, depending on the reactant concentrations (Fig. 3 and Supplementary Figs S35 and S36). For example, when the concentration of the AlBDC-3:2 gel is 0.05 mol l−1, the isotherm shows an H2-type hysteresis loop starting at P/P0=0.43. The mesoporous volume is ~0.76 cm3 g−1, with the mesopores exhibiting a narrow size distribution centred at ~5.4 nm. As the concentration increases to 0.15 mol l−1, the mesoporous volume significantly increases to ~2.25 cm3 g−1, and the pore size becomes larger and wider, centring around ~23.0 nm. The BET surface areas vary up to ~1,324 m2 g−1, in accordance with the contributions of the micro- and mesopore volumes, of which the total pore volume is mainly contributed by the mesopores at higher concentration. This is demonstrated by the fact that the hysteresis loops move and condense into higher pressure region (H1-type). At high concentration of 0.2 mol l−1, the pore sizes show significantly widened distribution at ~87.8 nm, which spans the meso- and macropore sizes. These results are indicative of remarkable influence of concentration on the texture and porosity of MOAs. A similar effect also can be observed for the AlBTC-1:1 and AlBTC-3:2 series (Supplementary Table S9); however, the concentration-pore-size dependency becomes less regular, probably as a result of mixed phases of the MOF particles.

Bottom Line: Developing a synthetic methodology for the fabrication of hierarchically porous metal-organic monoliths that feature high surface area, low density and tunable porosity is imperative for mass transfer applications, including bulky molecule capture, heterogeneous catalysis and drug delivery.Heating represents a key factor in the control of gelation versus crystallization of Al(III)-multicarboxylate systems.The porosity of the resulting metal-organic aerogels can be readily tuned, leading to the formation of well-ordered intraparticle micropores and aerogel-specific interparticle mesopores, thereby integrating the merits of both crystalline metal-organic frameworks and light aerogels.

View Article: PubMed Central - PubMed

Affiliation: MOE Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, Lehn Institute of Functional Materials, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275, China.

ABSTRACT
Developing a synthetic methodology for the fabrication of hierarchically porous metal-organic monoliths that feature high surface area, low density and tunable porosity is imperative for mass transfer applications, including bulky molecule capture, heterogeneous catalysis and drug delivery. Here we report a versatile and facile synthetic route towards ultralight micro/mesoporous metal-organic aerogels based on the two-step gelation of metal-organic framework nanoparticles. Heating represents a key factor in the control of gelation versus crystallization of Al(III)-multicarboxylate systems. The porosity of the resulting metal-organic aerogels can be readily tuned, leading to the formation of well-ordered intraparticle micropores and aerogel-specific interparticle mesopores, thereby integrating the merits of both crystalline metal-organic frameworks and light aerogels. The hierarchical micro/mesoporosity of the Al-metal-organic aerogels is thoroughly evaluated by N₂ sorption. The good accessibility of the micro/mesopores is verified by vapour/dye uptake, and their potential for utilization as effective fibre-coating absorbents is tested in solid-phase microextraction analyses.

No MeSH data available.