A Two-Dimensional Poly(azatriangulene) Covalent Organic Framework with Semiconducting and Paramagnetic States
Vellanki Lakshmi1, Cheng-Hao Liu1, Malakalapalli Rajeswara Rao1
1Department of Chemistry , McGill University , 801 Sherbrooke Street West , Montreal , Quebec , Canada H3A 0B8.
Abstract:
The black crystalline (aza)triangulene-based covalent organic framework TANG-COF was synthesized from its trinitro-TANG precursor via a one-pot, two-step reaction involving Pd-catalyzed hydrogenation and polycondensation with an aromatic dialdehyde. High crystallinity and permanent porosity of the layered two-dimensional (2D) structure were established. The rigid, electron-rich trioxaazatriangulene (TANG) building block enables strong π-electron interactions manifested in broad absorptions across the visible and NIR regions (Eg ≈ 1.2 eV). The high HOMO energy of TANG-COF (-4.8 eV) enables facile p doping, resulting in electrical conductivity of up to 10-2 S/cm and room-temperature paramagnetic behavior with a spin concentration of ∼10%. DFT calculations reveal dispersion of the highest occupied band both within the 2D polymer layers (0.28 eV) and along their π-stacked direction (0.95 eV).
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