Solution-Mediated Photoreversible Switch Between 2D and 3D Hydrogen-Bonded Organic Frameworks

In photoresponsive crystalline porous materials, the light-driven reversible topological transformation is of particular interest, as it can cause an overall change in structure and lead to more drastic switch in material properties, but remains a formidable challenge. Herein, we report a three-dimensional (3D) hydrogen-bonded organic framework (HOF-OF) self-assembled by photochromic diarylethene (DAE) and tetrakis(4-amidiniumphenyl)methane (TAM) via charge-assisted hydrogen bonds. Light irradiation drives isomerization of DAE, and the internal strain generated during photoisomerization is released through dissolution and recrystallization, which are accompanied by the breaking and reestablishment of hydrogen bonds. Benefit from the weak and reversible nature of hydrogen bonds as well as the good solution processability of HOFs, solution-mediated reversible switch between 3D and two-dimensional (2D) HOF is achieved by ring-open/ring-close photoisomerization of the DAE moiety controlled by remotely alternating UV and visible light irradiation. Loading lanthanide complex into HOF enables DAE photoisomerization-controlled photochromic fluorescence resonance energy transfer process between the lanthanide and DAE moiety, resulting in reversible luminescence on/off switch in the host-guest, capable of intelligent anti-counterfeiting in a noninvasive manner.