MOF for energy appl

nature chemistry 2010 0 000 87k des 020 040 060

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Unformatted text preview: Farha, et al., Nature Chemistry, 2010. 0 0.00 87K des 0.20 0.40 0.60 Pressure (atm ) 0.80 1.00 Goal: Enhance H2 uptake via framework reduction and cation doping • Enhanced London dispersion interactions due to enhanced strut polarizability? • Adsorption of polarizable molecules due to electric field enhancement? • Enhanced molecular adsorption due to charge/quadrupole interactions? The major technical and scientific challenge in this area is to increase the heat of adsorption of H2 to ca. 15-25 kJ/mol (to enable high loading at ambient temperature) A Computational Example: >5 wt. % at 300K! S. Han and W. A. Goddard III J. Am. Chem. Soc., 2007, 129, 8422–8423 (Mulfort, et al. Inorg. Chem. 2005) Framework reduction and cation doping Exploit organic struts within frameworks to introduce charge: enhance H2 binding and uptake Chemically reduce struts e- - - Charge compensating cations - induced dipole – induced dipole (strut) – (H2) - charge – quadrupole (cation) – (H2) Framework Reduction and Cation Doping a reducible-framework material (One of two identical networks shown) Observing Framework Reduction Solid state color changes mimic solution Zn2(NDC)2(diPyPI-Cl4) + CoCp2 Solid state EPR verifies presence of radicals EPR: Reduced MOF intensity Zn2(NDC)2(diPyNI) + Li(NAP) reduced with Li(NAP) reduced with CoCp 2 3400 3420 3440 3460 field (G) 3480 3500 Consequences of Framework Reduction… •N2 adsorption displays striking hysteresis w/5% lithium doping •Interpretation: nitrogen loading dependent conversion between interwoven and interpenetrated forms of the MOF structure 600 volume adsorbed (cm 3/mg) •Zn2(NDC)2(diPyNI) is reduced upon exposure to Li0 in DMF 500 400 300 200 100 0 0.0 1 1- Li+ 0.2 0.4 0.6 P/P o 0.8 1.0 Consequences of Framework Reduction… Hydrogen Adsorption •Zn2(NDC)2(diPyNI) is reduced upon exposure to Li0 in DMF Li+ •H2 uptake is nearly + Li0 doubled w/5% doping H2 wt% 1.6 with Li+ 1.2 0.8 no Li+ 0.4 0.0 0.0 0.2 0.4 0.6 P (atm)...
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