Photochromic crystalline hybrid materials with switchable properties: Recent advances and potential applications

The search for feasible strategies to construct molecular materials whose physical properties can be modulated dynamically by external stimuli, especially light for sunlight is the cleanest and most abundantly renewable energy source, has attracted increasing attention owing to their promising application in the field of detection, photo-electronic devices, information storage, etc. As a key branch, crystalline photochromic materials are usually formed by the combination of organic photoresponsive molecules and inorganic functional units. Under the stimuli of light, the changes of structures and some physical properties could occur, which provides a platform to develop photoswitching smart materials. To further promote the understanding and development of crystalline photochromic materials, in this review, we mainly focus on the representative smart photochromic hybrids with fast and stable multi-stimuli responsive behavior or with various switchable functions. In detail, in the first unit, the common design and synthesis strategy of crystalline photoresponsive materials will be demonstrated. The second section will introduce photochromic hybrids with novel structures and enhanced performance (multi-stimuli responsive, responsive rate). And the third section will present photochromic hybrids with photo-modulated luminescence (fluorescence, phosphorescence), photomagnetism, photoconductivity, photothermal conversion, or photoswitchable gas uptake behavior. Finally, the future challenges and opportunities for the development of photoresponsive smart hybrids will be addressed.