We report a new metal–organic framework, Fe-BTTri (Fe3[(Fe4Cl)3(BTTri)8]2·18CH3OH, H3BTTri =1,3,5-tris(1H-1,2,3-triazol-5-yl)benzene)), is found to be highly selective in the adsorption of CO over a variety of other gas molecules, making it extremely effective, for example, in the removal of trace CO from mixtures with H2, N2, and CH4. This framework not only displays significant CO adsorption capacity at very low pressures (1.45 mmol/g at just 100 μbar), but, importantly, also exhibits readily reversible CO binding. Fe-BTTri utilizes a unique spin state change mechanism to bind CO in which the coordinatively unsaturated, high-spin FeII centers of the framework convert to octahedral, low-spin FeII centers upon CO coordination. Desorption of CO converts the FeII sites back to a high-spin ground state, enabling the facile regeneration and recyclability of the material. This spin state change is supported by characterization via infrared spectroscopy, single crystal X-ray analysis, Mössbauer spectroscopy, and magnetic susceptibility measurements. Importantly, the spin state change is selective for CO and is not observed in the presence of other gases, such as H2, N2, CO2, CH4, or other hydrocarbons, resulting in unprecedentedly high selectivities for CO adsorption for use in CO/H2, CO/N2, and CO/CH4 separations and in preferential CO adsorption over typical strongly adsorbing gases like CO2 and ethylene. While adsorbate-induced spin state transitions are well-known in molecular chemistry, particularly for CO, to our knowledge this is the first time such behavior has been observed in a porous material suitable for use in a gas separation process. Potentially, this effect can be extended to selective separations involving other π-acids.
Reed, Douglas A., et al. "Reversible CO Scavenging via Adsorbate-Dependent Spin State Transitions in an Iron(II)–Triazolate Metal–Organic Framework." Journal of the American Chemical Society, vol. 138, no. 17, Apr. 2016. https://doi.org/10.1021/jacs.6b00248
Reed, Douglas A., Xiao, Dianne J., Gonzalez, Miguel I., Darago, Lucy E., Herm, Zoey R., Grandjean, Fernande, & Long, Jeffrey R. (2016). Reversible CO Scavenging via Adsorbate-Dependent Spin State Transitions in an Iron(II)–Triazolate Metal–Organic Framework. Journal of the American Chemical Society, 138(17). https://doi.org/10.1021/jacs.6b00248
Reed, Douglas A., Xiao, Dianne J., Gonzalez, Miguel I., et al., "Reversible CO Scavenging via Adsorbate-Dependent Spin State Transitions in an Iron(II)–Triazolate Metal–Organic Framework," Journal of the American Chemical Society 138, no. 17 (2016), https://doi.org/10.1021/jacs.6b00248
@article{osti_1387709,
author = {Reed, Douglas A. and Xiao, Dianne J. and Gonzalez, Miguel I. and Darago, Lucy E. and Herm, Zoey R. and Grandjean, Fernande and Long, Jeffrey R.},
title = {Reversible CO Scavenging via Adsorbate-Dependent Spin State Transitions in an Iron(II)–Triazolate Metal–Organic Framework},
annote = {We report a new metal–organic framework, Fe-BTTri (Fe3[(Fe4Cl)3(BTTri)8]2·18CH3OH, H3BTTri =1,3,5-tris(1H-1,2,3-triazol-5-yl)benzene)), is found to be highly selective in the adsorption of CO over a variety of other gas molecules, making it extremely effective, for example, in the removal of trace CO from mixtures with H2, N2, and CH4. This framework not only displays significant CO adsorption capacity at very low pressures (1.45 mmol/g at just 100 μbar), but, importantly, also exhibits readily reversible CO binding. Fe-BTTri utilizes a unique spin state change mechanism to bind CO in which the coordinatively unsaturated, high-spin FeII centers of the framework convert to octahedral, low-spin FeII centers upon CO coordination. Desorption of CO converts the FeII sites back to a high-spin ground state, enabling the facile regeneration and recyclability of the material. This spin state change is supported by characterization via infrared spectroscopy, single crystal X-ray analysis, Mössbauer spectroscopy, and magnetic susceptibility measurements. Importantly, the spin state change is selective for CO and is not observed in the presence of other gases, such as H2, N2, CO2, CH4, or other hydrocarbons, resulting in unprecedentedly high selectivities for CO adsorption for use in CO/H2, CO/N2, and CO/CH4 separations and in preferential CO adsorption over typical strongly adsorbing gases like CO2 and ethylene. While adsorbate-induced spin state transitions are well-known in molecular chemistry, particularly for CO, to our knowledge this is the first time such behavior has been observed in a porous material suitable for use in a gas separation process. Potentially, this effect can be extended to selective separations involving other π-acids.},
doi = {10.1021/jacs.6b00248},
url = {https://www.osti.gov/biblio/1387709},
journal = {Journal of the American Chemical Society},
issn = {ISSN 0002-7863},
number = {17},
volume = {138},
place = {United States},
publisher = {American Chemical Society (ACS)},
year = {2016},
month = {04}}
Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS); Energy Frontier Research Centers (EFRC) (United States). Center for Gas Separations Relevant to Clean Energy Technologies (CGS); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)
Sponsoring Organization:
National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
AC02-05CH11231; AC02-06CH11357; SC0001015
OSTI ID:
1387709
Alternate ID(s):
OSTI ID: 1259884
Journal Information:
Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 17 Vol. 138; ISSN 0002-7863
