Selective nitrogen adsorption via backbonding in a metal–organic framework with exposed vanadium sites


Industrial processes prominently feature π-acidic gases, and an adsorbent capable of selectively interacting with these molecules could enable important chemical separations1,2,3,4. Biological systems use accessible, reducing metal centres to bind and activate weakly π-acidic species, such as N2, through backbonding interactions5,6,7, and incorporating analogous moieties into a porous material should give rise to a similar adsorption mechanism for these gaseous substrates8. Here, we report a metal–organic framework featuring exposed vanadium(ii) centres capable of back-donating electron density to weak π acids to successfully target π acidity for separation applications. This adsorption mechanism, together with a high concentration of available adsorption sites, results in record N2 capacities and selectivities for the removal of N2 from mixtures with CH4, while further enabling olefin/paraffin separations at elevated temperatures. Ultimately, incorporating such π-basic metal centres into porous materials offers a handle for capturing and activating key molecular species within next-generation adsorbents.

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Fig. 1: Structural and spectroscopic characterization of V2Cl2.8(btdd).
Fig. 2: Characterization of the V–N2 interaction in V2Cl2.8(btdd).
Fig. 3: Assessment of N2/CH4 selectivity and N2 adsorption reversibility.
Fig. 4: Selective ethylene capture at high temperatures.

Data availability

The supplementary materials contain complete experimental and spectral details for all new compounds reported herein. Crystallographic data are available free of charge from the Cambridge Crystallographic Data Centre (CCDC). The CCDC numbers for the activated structure and for the N2-dosed structure are 1971589 and 1971588, respectively.


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The views and opinions of the authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. The synthesis of V2Cl2.8(btdd) was supported by the Hydrogen Materials—Advanced Research Consortium (HyMARC), established as part of the Energy Materials Network under the US Department of Energy (DoE), Office of Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office, under contract number DE-AC02-05CH11231, while its characterization by gas adsorption analysis, X-ray diffraction, infrared spectroscopy and NMR spectroscopy was supported by the US Department of Energy (DoE), Office of Science, Office of Basic Energy Sciences under award number DE-SC0019992. X-ray absorption spectroscopy experiments were supported by the Director, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences Heavy Elements Chemistry programme of the US DoE under contract number DE-AC02-05CH11231 (D.J.L. and D.K.S.), as well as the US DoE, Office of Science, Office of Basic Energy Sciences under award number DE-SC0016961 (M.W.M.), and data were collected with the X-ray absorption spectroscopy user resources of the Advanced Light Source, which is a DoE Office of Science User Facility under contract number DE-AC02-05CH11231. Powder X-ray diffraction data were collected at Beamline 17-BM at the Advanced Photon Source, a DoE Office of Science User Facility, operated by Argonne National Laboratory under contract number DE-AC02-06CH11357. We thank the National Science Foundation for graduate fellowship support of D.E.J., D.A.R. and J.O., the Philomathia Foundation and Berkeley Energy and Climate Institute for postdoctoral fellowship support of A.C.F. and Fondazione Banca del Monte di Lombardia - Progetto Professionalità Ivano Becchi 2016–2017 and University of Milan PSR 2017 for support of V.C. We are further grateful to the staff at the Biomolecular Technology Center of the California Institute for Quantitative Biosciences (QB3) at Berkeley for assistance with XPS measurements, D. J. Xiao, A. Turkiewicz, M. E. Ziebel, R. T. Torres-Gavosto and R. Bounds for helpful discussions and experimental assistance, and K. R. Meihaus for editorial assistance.

Author information

D.E.J., D.A.R. and J.R.L. formulated the project. D.E.J. and D.A.R. synthesized the materials. D.E.J. and D.A.R. collected and analysed the gas adsorption data. H.Z.H.J. collected and analysed the infrared spectra. D.E.J., J.O. and V.C. collected and analysed the X-ray diffraction data. M.W.M., D.J.L. and D.K.S. collected and analysed the X-ray absorption spectra. A.C.F., M.C. and J.A.R. collected and analysed the NMR spectra. R.A.M. collected and analysed the X-ray photoemission spectroscopy data. D.E.J., D.A.R. and J.R.L. wrote the manuscript, and all authors contributed to revising the manuscript.

Correspondence to Jeffrey R. Long.

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Competing interests

The authors declare the following competing interests: J.R.L. has a financial interest in Mosaic Materials, Inc., a start-up company working to commercialize metal−organic frameworks for gas separations. The University of California, Berkeley has applied for a patent on some of the technology discussed herein, on which J.R.L., D.E.J. and D.A.R. are listed as co-inventors.

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Supplementary information

Supplementary Information

Supplementary Discussion, Tables 1 and 2, Figs. 1–10 and refs. 1–12.

Crystallographic Data 1

Crystallographic information file for the N2-dosed structure.

Crystallographic Data 2

Crystallographic information file for the desolvated structure

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Jaramillo, D.E., Reed, D.A., Jiang, H.Z.H. et al. Selective nitrogen adsorption via backbonding in a metal–organic framework with exposed vanadium sites. Nat. Mater. (2020).

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