Host-guest strategy for full-visible-spectrum piezochromism in halogen-bonded organic frameworks

Full-visible-spectrum piezochromism is vital for advanced anti-counterfeiting and storage device applications, yet remains challenging. Polycyclic aromatic hydrocarbons represent a promising class of piezochromic materials. However, pressure-induced structural disorder severely limits their performance by causing photoluminescence (PL) quenching through energy dissipation. In framework materials, host-guest modes offer a promising avenue to overcome the limitations. Herein, we demonstrate that the halogen-bonded organic framework host incorporating acridine guests (denoted as XOF@AD) enables full-visible-spectrum piezochromism modulation with the PL red-shift of 237 nm during compression. Both experiments and calculations reveal that strengthened π-hole···π interactions lower its interaction energy to preserve the structural rigidity of XOF host. This suppresses the structural disorder of AD guests and maintains their enhanced π-π stacking interactions, which leads to a decreased band gap. This work establishes host-guest 3D-XOF as a superior platform that achieves full-visible-spectrum piezochromism and presents promising potential for pressure-responsive sensing.