Issue 1, 2021

Adsorption properties of acetylene, ethylene and ethane in UiO-66 with linker defects and NO2 functionalization

Abstract

Separation of small hydrocarbon gases is crucial for many industrial processes, but the high energy demand of current separation techniques encourages exploration of alternative sorption-based approaches. Here, we investigate the metal organic framework UiO-66(Zr) as possible solid adsorbent with a focus on the fundamental sorption mechanisms of C2 hydrocarbons in the presence of linker defects and NO2 functionalization. To this end, we directly measure heats of adsorption with calorimetry and correlate our results with ab initio calculations. In particular, we study adsorption of C2H2, C2H4 and C2H6 at 293 K and 195 K. At 293 K, the measured low-coverage enthalpy is found to be an average enthalpy of multiple adsorption sites. However, at 195 K, the low-coverage enthalpy corresponded to the strongest binding site, i.e. the linker defect site. We find that C2H2 exhibits the highest adsorption enthalpy with a significant gap of ∼6 kJ mol−1 to C2H4 and ∼9 kJ mol−1 to C2H6. Our ab initio calculations show excellent agreement with our experiments and are crucial to uncover the mechanisms that lead to the observed differences in binding affinity as a function of coverage. We also find that binding enthalpies increase for all three gases by adding –NO2 functional groups, which even further increase the gap to ∼9 kJ mol−1 and ∼10 kJ mol−1 for C2H4 and C2H6, respectively. Our findings provide mechanistic insight that suggests that linker defects in UiO-66(Zr) have promise to improve its effectiveness as a solid adsorbent in C2H2, C2H4 and C2H6 applications and that functionalization may be used to increase specificity.

Graphical abstract: Adsorption properties of acetylene, ethylene and ethane in UiO-66 with linker defects and NO2 functionalization

Supplementary files

Article information

Article type
Paper
Submitted
21 Sept. 2020
Accepted
05 Dec. 2020
First published
07 Dec. 2020
This article is Open Access
Creative Commons BY-NC license

Mater. Adv., 2021,2, 426-433

Adsorption properties of acetylene, ethylene and ethane in UiO-66 with linker defects and NO2 functionalization

H. Pandey, T. Barrett, M. D. Gross and T. Thonhauser, Mater. Adv., 2021, 2, 426 DOI: 10.1039/D0MA00722F

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