Direct observation of ammonia storage in UiO-66 incorporating Cu(II) binding sites

Yujie Ma, Wanpeng Lu, Xue Han, Yinlin Chen, Ivan Da Silva, Daniel Lee, Alena M. Sheveleva, Zi Wang, Jiangnan Li, Weiyao Li, Mengtian Fan, Shaojun Xu, Floriana Tuna, Eric J.L. Mcinnes, Yongqiang Cheng, Svemir Rudić, Pascal Manuel, Mark D Frogley, Anibal J. Ramirez-Cuesta, Martin Schroder

Research output: Contribution to journalArticlepeer-review

Abstract

The presence of active sites in metal-organic framework (MOF) materials can control and affect significantly their performance in adsorption and catalysis. However, revealing the interactions between substrate and active sites in MOFs with atomic precision remains a challenging task. Here, we report the direct observation of binding of NH3 in a series of UiO-66 materials containing atomically-dispersed defects and open Cu(I) and Cu(II) sites. While all MOFs in this series exhibit similar surface areas (1111-1135 m2 g−1), decoration of the −OH site in UiO-66-defect with Cu(II) results in a 43% enhancement of the isothermal uptake of NH3 at 273 K and 1.0 bar from 11.8 in UiO-66-defect to 16.9 mmol g−1 in UiO-66-CuII. A 100% enhancement of dynamic adsorption of NH3 at a concentration level of 630 ppm from 2.07 mmol g−1 in UiO-66-defect to 4.15 mmol g−1 in UiO-66-CuII at 298 K is observed. In situ neutron powder diffraction, inelastic neutron scattering, and electron paramagnetic resonance, solid-state nuclear magnetic resonance and infrared spectroscopies, coupled with modelling reveal that the enhanced NH3 uptake in UiO-66-CuII originates from {Cu(II)⋯NH3} interaction, with a reversible change in geometry at Cu(II) from near-linear to trigonal coordination. This work represents the first example of structural elucidation of NH3 binding in MOFs containing open metal sites, and will inform the design of new efficient MOF sorbents by targeted control of active sites for NH3 capture and storage.
Original languageEnglish
JournalAmerican Chemical Society. Journal
Publication statusAccepted/In press - 5 Apr 2022

Research Beacons, Institutes and Platforms

  • Photon Science Institute

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