Photogenerated Radical-Based Dual-Wavelength Responsive Photochromic Ionic Hydrogen-Bonded Organic Frameworks for...

Dual-wavelength response photochromic materials have attracted considerable attention due to their unique responsive characteristics and the synergistic enhancement of information security enabled by dual-dimensional (time-wavelength) control. We report a pair of chiral ionic hydrogen-bonded organic frameworks (R/S-iHOF-68) that exhibit dual-wavelength response photochromism through charge-assisted interaction. A two-dimensional supramolecular framework is co-constructed through mutual interactions between the electron donor (1R/S,2R/S)-1,2-diphenylethylenediamine (R/S-DPEN) and the electron-acceptor NDI derivatives (o-H2BSNDI). Upon irradiation with 275 nm and 365 nm, the crystal powder of R/S-iHOF-68 exhibits distinct photochromism, characterized by different rates of the photogenerated radical. This is attributed to the high sensitivity of the designed donor-acceptor (D-A) structure to the excitation energy of the different excitation wavelengths. To further explore the photophysical kinetic mechanism, we prepared suspensions (NMP, DMF, DMA), as well as R-iHOF-68@PVA membrane with different mass ratios. Upon 365 nm irradiation, the R/S-iHOF-68 suspensions exhibited a pronounced solvatochromic effect. The R-iHOF-68@PVA membrane demonstrated efficient photochromism, arising from the synergy between photogenerated radicals and Förster resonance energy transfer (FRET). A digital encoding strategy that integrates the binary code with the Morse code was developed to enhance the security of information storage. This multiform molecular encryption platform holds significant potential for high-security information encryption and real-time identity authentication in high-value applications.