Dithiine linkage formation via a dynamic and self-correcting nucleophilic aromatic substitution reaction enables the de novo synthesis of a porous thianthrene-based two-dimensional covalent organic framework (COF). For the first time, this organo-sulfur moiety is integrated as a structural building block into a crystalline layered COF. The structure of the new material deviates from the typical planar interlayer π-stacking of the COF to form undulated layers caused by bending along the C-S-C bridge, without loss of aromaticity and crystallinity of the overall COF structure. Comprehensive experimental and theoretical investigations of the COF and a model compound, featuring the thianthrene moiety, suggest partial delocalization of sulfur lone pair electrons over the aromatic backbone of the COF decreasing the band gap and promoting redox activity. Postsynthetic sulfurization allows for direct covalent attachment of polysulfides to the carbon backbone of the framework to afford a molecular-designed cathode material for lithium-sulfur (Li-S) batteries with a minimized polysulfide shuttle. The fabricated coin cell delivers nearly 77% of the initial capacity even after 500 charge-discharge cycles at 500 mA/g current density. This novel sulfur linkage in COF chemistry is an ideal structural motif for designing model materials for studying advanced electrode materials for Li-S batteries on a molecular level.
Bibliographical noteFunding Information:
This work was supported by the DFG Priority Programme “Polymer-based Batteries” (SPP 2248). The authors are grateful for the support from collaborative research center “Chemistry of Synthetic 2D Materials” funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)─SFB-1415-417590517. P.B. acknowledges the Alexander von Humboldt Foundation for funding. A.S. gratefully acknowledges the Fonds der Chemischen Industrie for a Liebig Fellowship. The X-ray photoelectron (XPS) data collection was performed at the EPSRC National Facility for XPS (“HarwellXPS”), operated by Cardiff University and UCL, under contract no. PR16195. Single-crystal X-ray diffraction data have been collected on BL14.2 at the BESSY II electron storage ring operated by the Helmholtz-Zentrum Berlin. We would particularly like to acknowledge the help and support of Dr. U. Mueller and Dr. Th. Hauß during the experiment. We thank the Center for Information Services and High-Performance Computing (ZIH) at TU Dresden for generous allocations of computer time. We also acknowledge the use of the facilities in the Dresden Center for Nanoanalysis (DCN) at the Technische Universität Dresden.
© 2022 American Chemical Society. All rights reserved.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry