Direct Construction of Magnetic and Electrical Two-Dimensional Radical Covalent Organic Frameworks

Radicals arranged in a two-dimensional (2D) hexagonal network can offer various exotic magnetic, electronic, and optical properties that find application in electronics/spintronics. However, direct synthesis remains challenging due to the scarcity of stable, symmetry-matched radical building blocks. Here, we report the bottom-up synthesis of hexagonal 2D radical covalent organic frameworks (RCOFs) with unpaired electrons at the nodes of the frameworks. A planar verdazyl radical amine (V-NH2) undergoes Schiff-base condensation with aldehydes to afford highly crystalline hexagonal RCOFs (VTPT and VPMT). The spin density was precisely controlled through the selection of building blocks with modulated spin-spin distances. The EPR and SQUID measurements confirmed a high spin concentration with antiferromagnetic interactions at low temperature, which is further tuned by interlayer interactions. Thin films of VTPT exhibited preferential in-plane orientation with enhanced photoconductivity, attributed to improved π-conjugation. These findings establish a direct route to RCOFs and underscore their potential as pseudo 1-dimensional antiferromagnetic materials. The direct synthesis of 2D radical covalent organic frameworks (RCOFs) from radical precursors remains a significant challenge. Here, the authors report the bottom up synthesis of hexagonal 2D RCOFs in which radical units are retained within the framework backbone.