Magnetic Properties and Magnetoresistance Effect of the Covalent Organic Frameworks with Stable Carbon-Centered...

Porous organic radical frameworks (PORFs), with their tunable topological architectures and distinct electronic properties, show exceptional promise for magnetic and spintronic applications. However, both integrating stable spin centers into π-conjugated porous frameworks and maintaining robust linkages pose significant synthetic challenges. In this work, two unprecedented C═C-linked radical frameworks are presented, PDA-PTMR and BTA-PTMR, engineered with distinct pore geometries. By anchoring stable polychlorotriphenylmethyl (PTM) radicals to the framework nodes, spin-½ paramagnetism in both systems is achieved. Remarkably, the PDA-PTMR framework exhibited a spin concentration of 5.45 × 10^{2 3} spins mol^-1, while both frameworks demonstrated intrinsic magnetic moments (S = 1/2) from unpaired electron spins. Density functional theory (DFT) calculations revealed the electronic structure and spin density distributions, uncovering the origin of their magnetic behavior. Furthermore, the fabrication of organic spin valves (OSVs) is pioneered using PORF films as active layers. The PDA-PTMR-based device displayed a magnetoresistance of -23% at 25 K, which is one of the highest values reported for the organic semiconductor-based OSVs. This study establishes a viable strategy for embedding magnetism in sp²-carbon-linked PORFs and provides a versatile platform for designing high-performance organic spintronic devices.