Ammonia‐Gated Guanyl Hydrazone Photoisomerization Enables Sequential Solid‐State Optical Response in Hydrogen‐Bonded Organic Frameworks

ABSTRACT

Light‐driven molecular switches enable precise and noninvasive regulation of molecular structure and function, and thus represent fundamental building blocks for stimuli‐responsive photofunctional materials. However, translating molecular‐level photoswitching into sequence‐dependent macroscopic outputs in the solid state remains a formidable challenge. In this study, we report a supramolecular strategy that integrates guanyl hydrazone switches into hydrogen‐bonded organic frameworks (HOFs) to overcome this limitation. A tetrasulfonate‐substituted tetraphenylethylene anion ( TPE ^{4 −} ) is employed as the host scaffold, while guanyl hydrazone ( G2 ) functions as the photoresponsive guest, affording a functional framework through cooperative assembly. This system leverages a reversible crystalline–amorphous phase transformation, triggered by acid–base stimuli, to gate the solid‐state photoisomerization of G2 . Upon activation, the configurational switching of G2 induces a cascade reorganization of the TPE ^{4 −} packing motifs, leading to pronounced and sequence‐dependent modulation of both fluorescence and macroscopic coloration. In addition, the applicability of this system in information encryption has been demonstrated. This work expands the design paradigm of hydrazone‐based photoswitches in the solid state and provides a supramolecular strategy for constructing intelligent optical materials with high information density and enhanced security.