Two-dimensional semiconducting covalent organic frameworks via condensation at arylmethyl carbon atoms.

Bi, Shuai; Yang, Can; Zhang, Wenbei; Xu, Junsong; Liu, Lingmei; Wu, Dongqing; Wang, Xinchen; Han, Yu et al. · Nat Commun · 2019

basic_science · Level V

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Abstract

Construction of organic semiconducting materials with in-plane π-conjugated structures and robustness through carbon-carbon bond linkages, alternatively as organic graphene analogs, is extremely desired for powerfully optoelectrical conversion. However, the poor reversibility for sp<sup>2</sup> carbon bond forming reactions makes them unavailable for building high crystalline well-defined organic structures through a self-healing process, such as covalent organic frameworks (COFs). Here we report a scalable solution-processing approach to synthesize a family of two-dimensional (2D) COFs with trans-disubstituted C = C linkages via condensation reaction at arylmethyl carbon atoms on the basis of 3,5-dicyano-2,4,6-trimethylpyridine and linear/trigonal aldehyde (i.e., 4,4″-diformyl-p-terphenyl, 4,4'-diformyl-1,1'-biphenyl, or 1,3,5-tris(4-formylphenyl)benzene) monomers. Such sp<sup>2</sup> carbon-jointed-pyridinyl frameworks, featuring crystalline honeycomb-like structures with high surface areas, enable driving two half-reactions of water splitting separately under visible light irradiation, comparable to graphitic carbon nitride (g-C<sub>3</sub>N<sub>4</sub>) derivatives.