Semiconducting Covalent Organic Frameworks based on Trioxotriangulene Neutral Radicals

Electrically conductive two-dimensional covalent organic frameworks (2D COFs) have emerged as a versatile class of crystalline porous polymers with promising applications in electronics and energy storage. However, high conductivities are typically achieved via post-synthetic doping to generate charge carriers, which can compromise crystallinity, porosity, and structural homogeneity. Persistent neutral organic radicals provide an attractive alternative, as their unpaired electrons can generate free charge carriers without the need for counterions. Herein, we report the design and synthesis of iminelinked 2D COFs incorporating stable trioxotriangulene (TOT) neutral radicals via two complementary synthetic approaches. Direct use of a TOT radical derivative functionalized with free amine groups affords a highly crystalline framework (TOT-COF-H) that exhibits semiconducting behavior (σRT = 1.2 × 10-4 S cm-1) and a reduced band gap (Eg = 1.07 eV). This work demonstrates a viable strategy for integrating stable neutral radical building blocks into COFs, enabling the development of intrinsically conductive, porous, and crystalline organic frameworks without the need for extrinsic doping.