Imagine you are driving on a highway at night. It's raining and the bright headlights of the car behind you are blinding you. How convenient it is to have
Recently, experts have found that, in addition to alreadyknown inorganic electrochromic materials, a new generation of highly ordered lattice structures - covalent organic frameworks (COFs) - can be equipped with this capability. Such materials are composed of synthetic organic building blocks. In suitable combinations, they form crystalline and nanoporous networks. Here, the color change can be caused by the applied voltage. It causes oxidation or reduction of the material.
A team of scientists from LMU led by ThomasBaina has developed COF structures whose switching speed and staining efficiency are many times higher than that of inorganic compounds. COFs are attractive in that their material properties are controlled over a wide range, as soon as their molecular building blocks are changed. Scientists at the LMU in Munich and the University of Cambridge have taken advantage of this to develop ideal COFs.
They used the modular design principleCOF and designed the perfect building block for our purposes with a specific thienoisoindigo molecule. Included in COF, the new component demonstrates how much it can enhance its properties. For example, the new material not only absorbs shorter wavelengths of ultraviolet light or small portions of the visible spectrum, but also achieves good near-infrared photoactivity.
At the same time, the new COF structures are much moresensitive to electrochemical oxidation. Even a low applied voltage is sufficient to cause a color change that is also completely reversible. This happens at a very high speed: the response time for a complete and distinct color change as a result of oxidation is about 0.38 seconds, recovery to original state is 0.2 seconds. This makes the electrochromic organic structures of the e-conversion team one of the fastest and most efficient in the world.
Research advances the development of a new classhighly effective electrochromic coatings. An obvious need for this is evident in the current applications of smart glass such as switchable sunscreens and sun-shaded windows for entire building facades.
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COF — Covalent Organic Frameworks