Abstract
© 2015 American Chemical Society. Simulations of H2 sorption were performed in a metal-organic framework (MOF) consisting of Zn$^{2+}$ ions coordinated to 1,2,4-triazole and tetrafluoroterephthalate ligands (denoted [Zn(trz)(tftph)] in this work). The simulated H2 sorption isotherms reported in this work are consistent with the experimental data for the state points considered. The experimental H2 isosteric heat of adsorption (Qst) values for this MOF are approximately 8.0 kJ mol$^{-1}$ for the considered loading range, which is in the proximity of those determined from simulation. The experimental inelastic neutron scattering (INS) spectra for H2 in [Zn(trz)(tftph)] reveal at least two peaks that occur at low energies, which corresponds to high barriers to rotation for the respective sites. The most favorable sorption site in the MOF was identified from the simulations as sorption in the vicinity of a metal-coordinated H2O molecule, an exposed fluorine atom, and a carboxylate oxygen atom in a confined region in the framework. Secondary sorption was observed between the fluorine atoms of adjacent tetrafluoroterephthalate ligands. The H2 molecule at the primary sorption site in [Zn(trz)(tftph)] exhibits a rotational barrier that exceeds that for most neutral MOFs with open-metal sites according to an empirical phenomenological model, and this was further validated by calculating the rotational potential energy surface for H2 at this site. (Figure Presented).
| Original language | English (US) |
|---|---|
| Pages (from-to) | 7328-7336 |
| Number of pages | 9 |
| Journal | Langmuir |
| Volume | 31 |
| Issue number | 26 |
| DOIs | |
| State | Published - Jun 24 2015 |
| Externally published | Yes |
Bibliographical note
KAUST Repository Item: Exported on 2020-10-01Acknowledged KAUST grant number(s): FIC/2010/06
Acknowledgements: The authors thank Zeric Hulvey for preparing a sample of [Zn(trz)(tftph)] and for his illuminating discussions on the INS spectra. B.S. acknowledges the National Science Foundation (Award No. CHE-1152362), the computational resources that were made available by a XSEDE Grant (No. TG-DMR090028), and the use of the services provided by Research Computing at the University of South Florida. This publication is also based on work supported by Award No. FIC/2010/06, made by King Abdullah University of Science and Technology (KAUST). The authors also thank the Space Foundation (Basic and Applied Research) for partial support. This work is based in part on experiments performed on the TOFTOF instrument operated by FRM-II at the Heinz Maier-Leibnitz Zentrum (MLZ), Garching, Germany. P.A.G. acknowledges support from the Project “Beyond Everest” under EU programme REGPOT-2011-1. This research project was also supported by the European Commission under the 7Framework Programme through the “Research Infrastructures” action of the “Capacities” Programme, NMI3-II Grant No. 283883.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.