MOFs H₂ Adsorption

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MOFs H₂ Adsorption

Summary:
The authors from Department of Chemistry, University of Michigan developed 8 metal-organic frameworks (MOFs) with different structural features (functionalized links, catenation, varied metal oxide units), achieving enhanced low-pressure H₂ adsorption (up to 9.8 H₂ per formula unit) in the application of hydrogen storage field.

Background:
1. To address the hydrogen storage bottleneck for transportation (inadequate physical storage methods), previous researchers studied microporous adsorbents like activated carbons and zeolites, yet MOFs (with high porosity) were rarely systematically studied for structure-adsorption relationships.
2. The authors proposed investigating effects of functionalization, catenation, and metal oxide variation on MOFs’ H₂ adsorption, obtaining insights into optimizing adsorption via structural design.

Research Content:
1.Synthesis: Used solvothermal method with metal nitrates and organic carboxylates as precursors; reacted in solvents (DMF, etc.) at 70-100℃ for 18-40h, followed by solvent activation and vacuum drying.
2.Characterizations:
   1) BET: IRMOF-20 (1507 m²/g), MOF-74 (783 m²/g); pore volume: IRMOF-20 (0.66 cm³/g), MOF-74 (0.39 cm³/g).
   2) XRD: Confirmed crystallinity (e.g., IRMOF-20 cubic structure, MOF-74 rhombohedral cell).
   3) Isosteric heat of adsorption: MOF-74 up to 8.3 kJ/mol, HKUST-1 2.0 kJ/mol higher than IRMOF-1 at low coverage.
3.Application: Tested H₂ adsorption at 77K/1atm; HKUST-1 adsorbed 25.4 mg/g, catenated IRMOF-13 had 33.5% pore filling.
4.Mechanism: Metal oxide units are key adsorption sites; catenation (pore constriction) and unsaturated metal sites enhance adsorption; large pore volume is prerequisite.

Outlook:
This research clarifies MOFs’ structure-H₂ adsorption relationships, provides design criteria for high-performance MOFs, and promotes progress in hydrogen storage materials.

Effects of Functionalization, Catenation, and Variation of the Metal Oxide and Organic Linking Units on the Low-Pressure Hydrogen Adsorption Properties of Metal-Organic Frameworks
Authors: Jesse L. C. Rowsell, Omar M. Yaghi*
DOI: 10.1021/ja056639q
Link: https://pubs.acs.org/doi/10.1021/ja056639q

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