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A New Approach to Enhancing the CO2 Capture Performance of Defective UiO-66 via Post-Synthetic Defect Exchange

preprint
revised on 11.01.2019 and posted on 11.01.2019 by Athanasios Koutsianos, Ewa Kazimierska, Andrew R. Barron, Marco Taddei, Enrico Andreoli
Zirconium-based metal-organic frameworks (Zr-MOFs) are a subclass of MOFs known for their remarkable stability, especially in the presence of water. This makes them extremely attractive for practical applications, including CO2 capture from industrial emission sources; however, the CO2 adsorption capacity of Zr-MOFs is moderate compared to that of the best performing MOFs reported to date. Functionalization of Zr-MOFs with amino groups has been demonstrated to increase their affinity for CO2. In this work, we assessed the potential of post-synthetic defect exchange (PSDE) as an alternative approach to introduce amino functionalities at missing-cluster defective sites in formic acid modulated UiO-66. Both pyridine-containing (picolinic acid and nicotinic acid) and aniline-containing (3-aminobenzoic acid and anthranilic acid) monocarboxylates were integrated within defective UiO-66 with this method. Non-defective UiO-66 modified with linkers bearing the same amino groups (2,5-pyridinedicarboxylic acid and 2-aminoterephthalic acid) were prepared by classical post-synthetic ligand exchange (PSE), in order to compare the effect of introducing functionalities at defective sites versus installing them on the backbone. PSDE reduces the porosity of defective UiO-66, but improves both the CO2 uptake and the CO2/N2 selectivity, whereas PSE has no effect on the porosity of non-defective UiO-66, improving the CO2 uptake but leaving selectivity unchanged. Modification of defective UiO-66 with benzoic acid reveals that pore size reduction is the main factor responsible for the observed uptake improvement, whereas the presence of nitrogen atoms in the pores seems to be beneficial for increasing selectivity.

Funding

The authors gratefully acknowledge the financial support provided by the Sêr Cymru Chair Programme (A.R.B.). The European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 663830 (M.T.), and the Engineering and Physical Sciences Research Council (EPSRC) for funding through the First Grant scheme EP/R01910X/1 (M.T.). The Welsh Government is also acknowledged for the Sêr Cymru II Recapturing Talent Fellowship (E.K.) partly funded by the European Regional Development Fund (ERDF). This work is also part of the Reduce Industrial Carbon Emissions (RICE) and Flexible Integrated Energy Systems (FLEXIS) operations funded by Welsh European Funding Office (WEFO), also partly funded by the ERDF. We would like to acknowledge the assistance provided by the Swansea University AIM Facility, which was funded in part by the EPSRC EP/M028267/1, the ERDF through the Welsh Government grant 80708, and the Sêr Solar project via the Welsh Government. Financial support was also provided the Robert A. Welch Foundation (C-0002).

History

Email Address of Submitting Author

marco.taddei@swansea.ac.uk

Institution

Swansea University

Country

United Kingdom

ORCID For Submitting Author

0000-0003-2805-6375

Declaration of Conflict of Interest

No conflict of interest

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