Dynamic Full‐Color Tuning of Organic Chromophore in a Multi‐Stimuli‐Responsive 2D Flexible MOF

Abstract

Developing universal stimuli-responsive materials capable of emitting a broad spectrum of colors is highly desirable. Herein, we deliberately grafted a conformation-adaptable organic chromophore into the established coordination space of a flexible metalorganic framework (MOF). In terms of the coupled structural transformations and the space confinement, the chromophore in the MOF matrix underwent wellregulated conformational changes under physical and chemical stimuli, simultaneously displaying thermo-, piezo-, and solvato-fluoro-chromism with color tunability over the visible range. Owing to the resilient nature and the reduced dimensionality of the selected coordination space, all three color modulations behaved in a sensitive and self-reversible manner, each following a linear correlation of the emission maximum with stimulus. Single-crystal X-ray diffraction of the variabletemperature structures and solvent-inclusion crystals elucidated the intricate color varying mechanisms.

Applications of Viologens in Organic and Inorganic Discoloration Materials

“…[7] Discoloration materials refer to the materials whose color changes due to external physical or chemical stimulation. Discoloration phenomena named for various stimuli include photochromism, [8] thermochromic, [9] electrochromism, [10] mechanical discoloration [11] and solvent discoloration. [12] Due to the potential application value of discoloration materials, they have attracted more and more attention.…”

Hydration-Facilitated Coordination Tuning of Metal–Organic Frameworks toward Water-Responsive Fluorescence and Proton Conduction

“…Metal–organic frameworks (MOFs) have received great attention because of the application potential in gas separation, catalysis, sensing, and proton conduction. − Especially, the advantage of MOF chemistry is the judicious choice of nodes and ligands as functional sites, − which allow for host–guest interactions to generate stimuli-induced readable signals in optics, magnetism, and conductivity, and a perfect platform for achieving stimuli-responsive materials can be promoted. − The ever-increasing demand for the versatile responsive material with more extensive applications, − such as chemical sensors, security writings, and smart optical displays, calls for the integration of different response modes into a single framework. , It has been approved that the interactions between functional sites of MOF and guests not only influence the intrinsic emission or energy transfer process of ligands and nodes − but also lead to the changes on signals of magnetism and conductivity. − However, reported multimode responsive MOFs are always achieved by the strong environmental stimulation, making it hard to keep the MOF structure stable and largely limit their practical applications.…”