Characterization of pore structure in metal-organic framework by small-angle X-ray scattering

Cheng Si Tsao*, Ming Sheng Yu, Tsui Yun Chung, Hsiu Chu Wu, Cheng-Yu Wang, Kuei Sen Chang, Hsin Lung Chen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

86 Scopus citations

Abstract

MOF-5-like crystals were studied by small-angle X-ray scattering (SAXS) to reveal, both quantitatively and qualitatively, their real structural details, including pore surface characteristics, pore shape, size distribution, specific surface area (SSA), spatial distribution, and pore - network structure. A combined SAXS and wide-angle X-ray scattering (WAXS) experiment was conducted to investigate the variation of the pore structure with the MOF-5 crystalline phase produced at different cooling rates. The SSA of the MOF-5 crystals synthesized herein spanned a broad range from ∼3100 to 800 m2/g. The real pore structures were divided into two regimes. In regime I the material consisted mainly of micropores of radius ∼8 Å as well as mesopores of radius 120∼80 Å. The structure in regime II was a fractal network of aggregated mesopores with radius ≥32 Å as the monomer, reducing SSA and hydrogen uptake capacity at room temperature. The two regimes can be manipulated by controlling the synthesis parameters. The concurrent evolution of pore structure and crystalline phase during heating for solvent removal was also revealed by the in-situ SAXS/WAXS measurement. The understanding of the impact of the real pore structure on the properties is important to establish a favorable synthetic approach for markedly improving the hydrogen storage capacity of MOF-5.

Original languageEnglish
Pages (from-to)15997-16004
Number of pages8
JournalJournal of the American Chemical Society
Volume129
Issue number51
DOIs
StatePublished - 26 Dec 2007

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