Chiral Covalent Organic Framework for Highly Efficient Spin Polarization

Two-dimensional chiral covalent organic frameworks (2D-CCOFs) stand out as excellent candidates for chiral spintronic devices owing to their tailorable semiconducting structures and intrinsic chiral sites. However, two critical challenges currently hinder their development: first, the difficulty in synthesizing highly crystalline 2D-CCOF films and, second, the lack of reliable methods to construct stable 2D-CCOF-based spintronic devices. Herein, we successfully synthesized a 2D-CCOF film featuring a high crystallinity and excellent conductivity. In situ magnetic conductive-probe AFM (in situ mCP-AFM) characterization confirms that this 2D-CCOF exhibits excellent chiral-induced spin selectivity (CISS), with a spin polarization over 90% at room temperature. Using graphene as a blocking layer, we have successfully constructed stable half-spin valve devices based on the 2D-CCOF, which exhibit distinct chirality-dependent magnetoresistance. Graphene plays a key role in mitigating the detrimental effect of electrode deposition on the CCOF films. The excellent spin selectivity of 2D-CCOF opens up unprecedented opportunities for efficient control of electron spin and enables solid-state chiral spintronic devices.