Naphthalenediimide-based photochromic MOFs: Structure visualization upon radical formation, and applications in purple light detection, inkless printing and anti-counterfeiting.

A Naphthalenediimide-based photochromic 2D MOF was successfully synthesized. After irradiation and immersion in acetonitrile solution, the single-crystal-to-single-crystal transition occurred, and 1-P and 1@MeCN were obtained, respectively. 1-P is a rare example of structural visualization during the formation of free radicals after NDI-based photochromism. 1@MeCN improves the photochromic performance of the system by introducing solvent molecules. Finally, for the first time, 1@MeCN was combined with organic glass for practical applications in ink-free printing, purple light detection/filtering, and information anti-counterfeiting. [Display omitted] • A photochromic MOF (1) based on the NDI ligand was synthesized and characterized. • Captured a rare process of structural visualization of free radical formation in 1-P. • The effect of solvent on the photochromic properties (1@MeCN) was revealed. • 1 and 1@MeCN were first used to selectively detect and filter 395 nm purple light. • The 1@MeCN glass was prepared for the first time. It is still a great challenge to understand the structural variation during the photochromic process, to rationally regulate the photochromic performance, and to expand the practical application of NDI-based photochromic materials. Herein, we found a 2D NDI-type photochromic MOF (1). When illuminated by 395 nm purple light, 1 underwent a single-crystal-to-single-crystal (SCSC) transition, resulting in 1-P , which is a rare structural visualization phenomenon during the formation of free radicals. In addition, it was demonstrated for the first time that the introduction of solvent molecules into the system (1@MeCN) can modulate the photochromic ability caused by electron transfer. It was found that 1 and 1@MeCN have the most sensitive response to 395 nm purple light, and are ideal candidates for detecting and filtering purple light. Finally, a photochromic glass based on 1@MeCN was reported, which is first applied in ink-free printing, purple light detection/filtering, and information anti-counterfeiting. [ABSTRACT FROM AUTHOR]