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Two-dimensional sp2 carbon–conjugated covalent organic frameworks

We synthesized a two-dimensional (2D) crystalline covalent organic framework (sp2c-COF) that was designed to be fully -conjugated and constructed from all sp2 carbons by C=C condensation reactions of tetrakis(4-formylphenyl)pyrene and 1,4-phenylenediacetonitrile. The C=C linkages topologically connect pyrene knots at regular intervals into a 2D lattice with conjugations extended along both x and y directions and develop an eclipsed layer framework rather than the more conventionally obtained disordered structures. The sp2c-COF is a semiconductor with a discrete band gap of 1.9 electron volts and can be chemically oxidized to enhance conductivity by 12 orders of magnitude. The generated radicals are confined on the pyrene knots, enabling the formation of a paramagnetic carbon structure with high spin density. The sp2 carbon framework induces ferromagnetic phase transition to develop spin-spin coherence and align spins unidirectionally across the material.

Authors:   Enquan Jin; Mizue Asada; Qing Xu; Sasanka Dalapati; Matthew A. Addicoat; Michael A. Brady; Hong Xu; Toshikazu Nakamura; Thomas Heine; Qiuhong Chen; Donglin Jiang
Journal:   Science
Volume:   357
edition:   6352
Year:   2017
Pages:   673
DOI:   10.1126/science.aan0202
Publication date:   18-Aug-2017
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