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In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Covalent organic frameworks are a type of crystalline porous materials that linked through covalent bond, and they have numerous potential applications in adsorption, separation, catalysis, and more. However, there are rarely relevant reported on photochromism.
Furthermore, the reason of photochromic process is discussed by electron paramagnetic resonance, X-ray photoelectron spectroscopy, electrochemistry characterizations and transient absorption measurements. This work expands a stable organic photochromic material and broadens the applications of COFs. In the past decade, there was a lot of attention given to photochromic materials that respond to color changes in the light stimulus and usually reversible 1 , 2 , 3 , 4 , 5 , owing to their attractive applications include switching, logic gates, anticounterfeiting, information storage, optoelectronic devices, environmental monitoring, superior bioimaging, and so forth 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , Nowadays, a number of inorganic, organic and inorganic-organic hybrid photochromic materials have been explored 5 , 15 , 16 , The common inorganic photochromic materials include polyoxometalates, transition metal oxides, metal halides, prussian blue analogs and rare earth complexes, etc.
The classic organic photochromic materials contain dithienylethene, spiropyrans, diarylethenes, chromenes, fulgides, azocompounds, viologens, and so on. The inorganic-organic hybrid photochromic materials cover hybrids of metal halides, hybrids of metal cyanides, hybrids of polyoxometalates, metal chalcogenide, and metal-organic complexes, etc. The photochromism are mainly due to the change oxidation states upon irradiation, photo-induced molecular conformations isomerization, polarity, and photoinduced electron transfer 18 , 19 , 20 , 21 , Design and synthesis of stable photochromic materials featuring fast response and high contrast are still a challenging task 23 , As a recently emerging class of porous crystalline materials assembled through strong covalent bonds, covalent organic frameworks COFs have become attractive platforms for various functional materials, including gas adsorption and storage, energy storage and conversion, drug delivery, and heterogeneous catalysis owing to their unique features including permanent porosity, low densities, and high surface areas.
These advantages enable COFs to readily adsorb guest molecules and establish interactions with them. The more important thing is COFs have relatively high chemical, light and thermal stabilities, which make them more suitable for practical applications 25 , 26 , 27 , However, there is no report other type photochromic COF.
