Effect of ring rotation upon gas adsorption in SIFSIX-3-M (M = Fe, Ni) pillared square grid networks
The study of the mobility/rotation of the organic linkers in porous metal-organic frameworks could provide a valuable information about the guest/framework interaction and the factors control the kinetics of adsorption. Here, we analyzed the dynamics of pyrazine ring rotation in a series of pillared square grid frameworks, namely SIFSIX-3-M (M = Fe, Ni). It was found that the rotation of pyrazine ring is influenced by the variation of metal cation, temperature and the guest molecule. The Fe-analogue, [Fe(pz)2(SiF6)2] (pz= Pyrazine), , showed no pronounced ring rotation and exhibited a high affinity toward Xe gas over Kr as exemplified by the sharp Xe uptake at low loading (~0.1 bar) and its high isosteric heat of adsorption (Qst~ 27.4 kJmol-1) compared to the current benchmark materials. The Ni analogue, on the contrary, showed a two-regime adsorption isotherm for Xe with a temperature-dependent inflection point. However, this behavior is not observed with the other gases such as CO2, N2, and Kr which showed one-step adsorption isotherms without any inflection. Using molecular models and simulations, we hypothesize that the inflection point is due to a disordered to ordered transition of the rotational configurations of the pz rings in SIFSIX-3-Ni. These results further support the impact of tuning the pore size and chemistry on the adsorption behavior of porous materials.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- USDOE Office of Nuclear Energy (NE)
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1373592
- Journal Information:
- Chemical Science, Journal Name: Chemical Science Journal Issue: 3 Vol. 8; ISSN 2041-6520
- Publisher:
- Royal Society of Chemistry
- Country of Publication:
- United States
- Language:
- English
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