Reference : Hydrogen Storage and Carbon Dioxide Capture in an Iron-Based Sodalite-Type Metal-Organic...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Chemistry
Hydrogen Storage and Carbon Dioxide Capture in an Iron-Based Sodalite-Type Metal-Organic Framework (Fe-BTT) Discovered via High-Throughput Methods
Sumida, Kenji [> > > >]
Horike, S [> > > >]
Kaye, S.S. [> > > >]
Herm, Zoey [> > > >]
Queen, Wendy [> > > >]
Brown, Craig M [> > > >]
Grandjean, Fernande mailto [Université de Liège - ULg > Département de physique > Département de physique >]
Long, Gary J mailto [> > > >]
Daily, Ann [> > > >]
Long, Jeffrey R. [> > > >]
Chemical Science
Royal Society of Chemistry
[en] hydrogen storage ; Mossbauer spectroscopy ; neutron diffraction
[en] Using high-throughput instrumentation to screen conditions, the reaction between FeCl2 and H3BTT.2HCl(BTT3-=1,3,5-benzenetristetrazolate) in a mixture of DMF and DMSO was found to afford Fe3[(Fe4Cl)3(BTT)8]2.22DMF.32DMSO.11H2O. THis compound adopts a porous three-dimensional framework structure consisting of squre [Fe4CL]2+ units linked via triangulat BTT3- bridging ligands to give an anionic 3.8-net. Mossbauer spectroscopy carried out on a DMF-solvated version of the material indicated the framework to contain high-spin Fe2+ with a distribution of local environments and confirmed the presence of extra-framework iron cations. Upon soaking the compound in methanol and heating at 135 C for 24 h under dynamic vacuum, most of the solvent is removed to yield Fe3[(Fe4Cl)3(BTT)8(MeOH)4]2(Fe-BTT), a microporous solid with a BET surface area of 2010 m2g-1 and open Fe2+ coordination sites. Hydrogen adsorption data collected at 77 K show a steep rise in the isotherm, associated with an initial isosteric heat of adsorption of 11.9 kJ/mol, leading to a total storage capacity of 1.1 wt% and 8.4 g/L at 100 bar and 298 K. Powder neutron diffraction experiments performed at 4 K under various D2 loadings enabled identification of ten different adsorption sites. with the strongest binding site residing just 2.17(5) Å from the framework Fe2+ cation. Inelastic neutron scattering spectra are consistent with the strong rotational hindering of the H2 molecules at low loadings, and further reveal the catalytic conversion of ortho-H2 to para-H2 by the paramagnetic iron centers. The exposed Fe2+ cation sites within Fe-BTT also lead to the selective adsorption of CO2 over N2, with isotherms collected at 298 K indicating uptake ratios of 30.7 and 10.8 by weight at 0.1 and 1.0 bar, respectively.

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