Twisted node modulation of 2D-COFs for programmable long-afterglow luminescence

Controlled interlayer stacking, solvent processing, and long-afterglow luminescence have been challenges in the development of two-dimensional covalent organic frameworks (2D-COFs). We propose a twisted node modulation strategy to address these issues simultaneously. Consistency of node distortion types causes stacking style to become non-adjustable: eclipsed stacking (non-twisted node) and inclined stacking (twisted node). By alternating the introduction of twisted and non-twisted nodes into a 2D-COFs system, a reversible crystal transformation between eclipsed and inclined stacking is achieved. The inclined COFs can be easily exfoliated into nanosheets for solution processing. Confining isolated exfoliated nanosheets within the polymethyl methacrylate achieves programmable long-afterglow luminescence, which is for writing and printing, as well as imaging, anti-counterfeiting, and emergency lighting. This work provides a strategy for the design of 2D-COFs with different stackings to address the challenges of difficult processing for novel functional applications.