Chiral two-dimensional conjugated metal-organic frameworks with high spin polarization

Two-dimensional conjugated metal-organic frameworks have garnered significant research interest as emerging candidates for organic 2D crystal materials. In classical 2D crystals, chirality can give rise to unique physical phenomena; however, the precise implantation of chirality into 2D c-MOFs has yet to be demonstrated. Here, we demonstrate an example of chiral 2D c-MOFs obtained through the side chain-induced chirality amplification strategy to achieve tunable chiral expression, enabling notable chirality amplification. Chiral substitutions induce distortions in the 2,3,7,8,12,13-hexaiminotriindole conjugated ligand along distinct orientations, effectively transferring their chirality to the conjugated backbone. The resulting frameworks exhibit tunable chirality through steric control, where chiral naphthylethyl substitution increases the distortion angle from 2.3° to 7.0°, leading to pronounced chirality amplification. Furthermore, the chiral 2D c-MOFs demonstrate exceptional spin polarization measured by magnetic-conductive atomic force microscopy (mc-AFM), achieving a value as high as 96.9%, placing them among the highest-performing materials reported to date. This work opens new avenues for the design of chiral 2D crystal materials with potential applications in chiral spintronics.