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Structures and H2 Adsorption Properties of Porous Scandium Metal–Organic Frameworks

DOI: 10.1002/chem.201000926 DOI Help
PMID: 20960440 PMID Help

Authors: Ilich Ibarra (University of Nottingham) , Xiang Lin (University of Nottingham) , Sihai Yang (University of Nottingham) , Gavin S. Walker (University of Nottingham) , Sarah A. Barnett (Diamond Light Source) , David R. Allan (Diamond Light Source) , Neil R. Champness (University of Nottingham) , Peter Hubberstey (University of Nottingham) , Martin Schroeder (University of Nottingham) , Alexander J. Blake (University of Nottingham)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemistry - A European Journal

State: Published (Approved)
Published: October 2010

Abstract: Two new three-dimensional ScIII metal-organic frameworks {[Sc3O(L1)3(H2O)3]-Cl0.5(OH)0.5(DMF)4(H2O)3}∞(1) (H2L1=1,4-benzene-dicarboxylic acid) and {[Sc3O(L2)2(H2O)3](OH)(H2O)5(DMF)}∞(2) (H3L2=1,3,5-tris(4-carboxyphenyl)benzene) have been synthesised and characterised. The structures of both 1 and 2 incorporate the trinuclear trigonal planar [Sc3(O)(O2CR)6] building block featuring three ScIII centres joined by a central μ3-O2-; donor. Each ScIII centre is further bound by four oxygen donors from four different bridging carboxylate anions, and a molecule of water located trans to the μ3-O2- donor completes the six coordination at the metal centre. Frameworks 1 and 2 show high thermal stability with retention of crystallinity up to 350°C. The desolvated materials 1a and 2a, in which the solvent has been removed from the pores but with water or hydroxide remaining coordinated to ScIII, show BET surface areas based upon N2 uptake of 634 and 1233m2g^-1, respectively, and pore volumes calculated from the maximum N2 adsorption of 0.25cm3g^-1 and 0.62cm3g^-1, respectively. At 20 bar and 78K, the H2 isotherms for desolvated 1a and 2a confirm 2.48 and 1.99wt% total H2 uptake, respectively. The isosteric heats of adsorption were estimated to be 5.25 and 2.59kJmol^-1 at zero surface coverage for 1a and 2a, respectively. Treatment of 2 with acetone followed by thermal desolvation in vacuo generated free metal coordination sites in a new material 2b. Framework 2b shows an enhanced BET surface area of 1511m2^-1 and a pore volume of 0.76cm3g^-1, with improved H2 uptake capacity and a higher heat of H2 adsorption. At 20 bar, H2 capacity increases from 1.99wt% in 2a to 2.64wt% for 2b, and the H2 adsorption enthalpy rises markedly from 2.59 to 6.90kJmol^-1.

Journal Keywords: Carboxylate Ligands; Coordination Polymers; Free Metal Coordination Sites; Hydrogen; Scandium

Subject Areas: Chemistry

Instruments: I19-Small Molecule Single Crystal Diffraction

Added On: 21/10/2010 13:41

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