Hydrogen storage and carbon dioxide capture in an iron-based sodalite-type metal-organic framework (Fe-BTT) discovered via high-throughput methods

作者：Sumida Kenji; Horike Satoshi; Kaye Steven S; Herm Zoey R; Queen Wendy L; Brown Craig M; Grandjean Fernande; Long Gary J; Dailly Anne; Long Jeffrey R^*

来源：Chemical Science, 2010, 1(2): 184-191.

DOI：10.1039/c0sc00179a

Using high-throughput instrumentation to screen conditions, the reaction between FeCl2 and H3BTT center dot 2HCl (BTT(3-) = 1,3,5-benzenetristetrazolate) in a mixture of DMF and DMSO was found to afford Fe(3)[(Fe(4)Cl)(3)(BTT)(8)](2)center dot 22DMF center dot 32DMSO center dot 11H(2)O. This compound adopts a porous three-dimensional framework structure consisting of square [Fe(4)Cl](7+) units linked via triangular BTT(3-) 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 Fe(2+) 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 degrees C for 24 h under dynamic vacuum, most of the solvent is removed to yield Fe(3)[(Fe(4)Cl)(3)(BTT)(8)(MeOH)(4)](2) (Fe-BTT), a microporous solid with a BET surface area of 2010 m(2) g(-1) and open Fe(2+) 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(-1), leading to a total storage capacity of 1.1 wt% and 8.4 g L(-1) at 100 bar and 298 K. Powder neutron diffraction experiments performed at 4 K under various D(2) loadings enabled identification of ten different adsorption sites, with the strongest binding site residing just 2.17(5) angstrom from the framework Fe(2+) cation. Inelastic neutron scattering spectra are consistent with the strong rotational hindering of the H(2) molecules at low loadings, and further reveal the catalytic conversion of ortho-H(2) to para-H(2) by the paramagnetic iron centers. The exposed Fe(2+) cation sites within Fe-BTT also lead to the selective adsorption of CO(2) over N(2), 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.

• 出版日期2010