Supramolecular Chiral Halogen-Bonded Organic Frameworks Enhance Efficient Chirality-Induced Spin Selectivity.

Chirality-induced spin selectivity (CISS) has attracted extensive interest for its various potential applications. However, the development of high-spin-polarization CISS materials still represents a significant challenge. We report the design and preparation of two novel 2D chiral halogen-bonded organic frameworks (XOFs), XOF-TPH and XOF-TPO, constructed from chiral binaphthyl crown ether-based ligands. By modulating the crown ether size, we controlled the molecular flexibility and consequently the crystallinity of the XOFs. The formation of XOF-TPH/TPO was characterized by 1H NMR, XPS, IR, XAFS, PXRD, SAXS, HR-TEM, and SEAD. The frameworks exhibited pronounced Cotton effects and magnetic circular dichroism (CD), confirming their chiral nature. XOF-TPH/TPO exhibited superior charge-transport capability over the ligands. More importantly, both XOFs demonstrated significantly enhanced CISS effects compared to the monomeric ligands. This enhancement was attributed to the well-ordered framework structures and the heavy-atom effect of iodine, which amplifies spin-orbit coupling. Notably, XOF-TPH, with higher crystallinity, exhibited remarkable CISS performance with a spin polarization up to 94%, implying the crucial role of structural order. This work showed the tremendous potential of chiral XOFs for high spin selectivity and offered valuable insights into the structure-property relationship within CISS, which is crucial for the development of high-performance CISS materials.