Abstract
Porous graphitic framework (PGF) is a two-dimensional (2D) material that has emerging energy applications. An archetype contains stacked 2D layers, the structure of which features a fully annulated aromatic skeleton with embedded heteroatoms and periodic pores. Due to the lack of a rational approach in establishing in-plane order under mild synthetic conditions, the structural integrity of PGF has remained elusive and ultimately limited its material performance. Here, we report the discovery of the unusual dynamic character of the C=N bonds in the aromatic pyrazine ring system under basic aqueous conditions, which enables the successful synthesis of a crystalline porous nitrogenous graphitic framework with remarkable in-plane order, as evidenced by powder X-ray diffraction studies and direct visualization using high-resolution transmission electron microscopy. The crystalline framework displays superior performance as a cathode material for lithium-ion batteries, outperforming the amorphous counterparts in terms of capacity and cycle stability. Insertion of well-defined, evenly spaced nanoscale pores into the two-dimensional (2D) layers of graphene invokes exciting properties due to the modulation of its electronic band gaps and surface functionalities. A bottom-up synthesis approach to such porous graphitic frameworks (PGFs) is appealing but also remains a great challenge. The current methods of building covalent organic frameworks rely on a small collection of thermodynamically reversible reactions. Such reactions are, however, inadequate in generating a fully annulated aromatic skeleton in PGFs. With the discovery of dynamic pyrazine formation, we succeeded in applying this linking chemistry to obtain a crystalline PGF material, which has displayed high electrical conductivity and remarkable performance as a cathode material for lithium-ion batteries. We envision that the demonstrated success will open the door to a wide array of fully annulated 2D porous frameworks, which hold immense potential for clean energy applications. We report the unusual dynamic characteristics of the C=N bonds in the pyrazine ring promoted under basic aqueous conditions, which enables the successful synthesis of two-dimensional porous graphitic frameworks (PGFs) featuring fully annulated aromatic skeletons and periodic pores. The PGF displayed high electrical conductivity and remarkable performance as a cathode material for lithium-ion batteries, far outperforming the amorphous counterparts in terms of capacity and cycle stability.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 933-944 |
| Number of pages | 12 |
| Journal | Chem |
| Volume | 6 |
| Issue number | 4 |
| DOIs | |
| State | Published - Apr 9 2020 |
| Externally published | Yes |
Bibliographical note
KAUST Repository Item: Exported on 2022-06-14Acknowledgements: Work at the Molecular Foundry was supported by the Office of Science and Office of Basic Energy Sciences of the U.S. Department of Energy under contract no. DE-AC02-05CH11231. S.C. and B.S. are grateful for the support from the National Natural Science Foundation of China (grant no. 21603076 and 21802128, respectively). H.Z. thanks the funding support from the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division under contract no. DE-AC02-05-CH11231 within the program of KC22ZH. We thank Virginia Altoe, Changlin Zhang, Chongqing Yang, Liana M. Klivansky, and Teresa Chen from the Molecular Foundry; Professor Yu Han from KAUST for their help on structural characterizations; and Professor Yi Cui from Stanford University for his support on battery characterization. We thank Stephen Whitelam and Zdenek Preisler from the Molecular Foundry for help with initial modeling. We also thank Dr. Hassan Celik, Dr. Nanette Jarenwattananon, and the SSNMR facility from the Department of Chemical and Biomolecular Engineering, University of California Berkeley for assistance with solid-state NMR measurements. Yi Liu, J.Z. E.M.C. J.C. and J.J.U. conceived the project. Yi Liu designed the experiments, X.L. H.W. and H.C. conducted the experiments and analyses. Q. Zheng, Q. Zhang, and Yawei Liu performed and with H.Z. interpreted TEM measurements. H.M. conducted and with J.A.R. interpreted solid-state NMR measurements. S.C. performed PXRD simulations and analysis. B.S. assisted with figure revisions, Raman, and AFM measurements. C.D. and M.P.G. assisted with electrical conductivity measurements. Yi Liu, E.M.C. J.C. J.J.U. X.L. H.W. and H.C. wrote and revised the manuscript. All authors discussed the results and commented on the manuscript. X.L. H.W. H.C. and Q. Zheng contributed equally to this work. A patent application related to PGF-1 is pending.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.
