ChemRxiv
These are preliminary reports that have not been peer-reviewed. They should not be regarded as conclusive, guide clinical practice/health-related behavior, or be reported in news media as established information. For more information, please see our FAQs.
1/1
0/0

Post-synthetic ligand exchange in zirconium-based metal-organic frameworks: beware of the defects!

preprint
revised on 14.06.2018 and posted on 14.06.2018 by Marco Taddei, Russell J. Wakeham, Athanasios Koutsianos, Enrico Andreoli, Andrew R. Barron

Post-synthetic ligand exchange in the prototypical zirconium-based metal-organic framework UiO-66 was investigated by in situ solution 1H nuclear magnetic resonance. Samples of UiO-66 having different degrees of defectivity were exchanged using solutions of several terephthalic acid analogues in a range of conditions. Linker exchange only occurred in defect-free UiO-66, whereas monocarboxylates grafted at defective sites were found to be preferentially exchanged with respect to terephthalic acid over the whole range of conditions investigated. A 1:1 exchange ratio between the terephthalic acid analogue and modulator was observed, providing evidence that the defects had missing-cluster nature. Ex situ characterisation of the MOF powders after exchange corroborated these findings and evidenced that the physical-chemical properties of the MOF depend on whether the functionalisation occurs at defective sites or on the framework. N2 sorption analysis showed that, upon exchange, defective samples underwent significant decrease of surface area and disappearance of large pores, associated with the presence of missing-cluster defects in the starting material. CO2 sorption studies displayed the different impact of pure defect functionalisation and pure framework functionalisation on isosteric heat of adsorption and CO2/N2 selectivity.

Funding

European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 663830; Welsh Government Sêr Cymru Programme; FLEXIS; 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

There are no conflicts to declare.

Version Notes

Manuscript: added stacked NMR primary data to Figure 2. Supporting Information: added SEM pictures and stacked primary NMR data. Amended discussion regarding the kinetic analysis for BA_mod.

Exports