Syntheses, Structures And Properties Of Novel Photochromic Open-framework Mateirals

Zeolite-based open-framework materials have been widely used in catalysis,adsorption–separation, ion exchange and host-guest assembly due to their uniformnanosize pores, large specific surface area, high thermal stability and chemicalstability, and tunable chemical compositions and pore structures. Moreover, a varietyof metal doped open-framework materials endow them specific physical andchemical properties, such as luminescence, electricity, magnetism, etc. Thus, thesearch for new inorganic open-framework materials with novel functions andstructures has become a continuous interest in the field of zeolite science.Photochromic materials have attracted much attention because of their real orpotential applications in the felds of protection (in spectacles, photobarriers,anti-fake, and camoufage), decoration, display, memory, switches, photography,photometry, photomechanics, and so on. Growing interest in this feld has largelyexpanded the research of photochromic materials for the purpose of improvingexisted photochromic materials, fabricating photoresponsive devices, and exploringnew families of photochromic materials. Compared with the well studied organicphotochromic compounds, the inorganic photochromic materials are relatively rare.Introducing organic photochromic components into the inorganic open frameworksmay facilicate the preparation of new family of inorganic photochromic materials.In this thesis, we have solvothermally synthesized three novel photochromicmetal phosphates with open-framework or zeolite structures by using in-situgenerated methylviologen as the organic templates, and studied their photochromicbehaviors, as well as their reversible photovoltaic activity and photoluminescence.Finally, we have discussed the interaction between anionic frameworks and methylviologen dication (MV2+) in these three compounds, revealing therelationship between the synthesis, structure and properties. The main results are asfollows:1. The second example of inorganic open-framework crystalline material JU98has been synthesized by using methylviologen (MV) as the template. Itpossesses a unique pillar–layered structure with12-ring channels. JU98exhibits reversible photochromic properties varying from colorless to blueunder UV irradiation. The crystalline anionic framework afects thephotoinduced color change of encapsulated MV2+cations. Furthermore,reversible photovoltaic activity and photoluminescence property of JU98areobserved. FISPS study reveals the n-type semiconductor character of JU98.This work will promote the exploration of more viologen-based inorganicopen-framework materials, and is also important for the design of newmultifunctional optical and semiconducting materials.2. A novel X-ray-induced photochromic material JU99based onmethylviologen has been prepared. It shows rapid response to X-rayirradiation at room temperature, and the coloration-decoloration process isreversible by alternated X-ray irradiation and heating treatment whilekeeping the structure unchanged. More interestingly, JU99also exhibitsphotoluminescence and photovoltaic properties, which can be regulated byX-ray irradiation. Noticed that the acute toxic MV was in-situ synthesizedunder the solvothermal condition, and a new path for recycling MV has beendeveloped by the convenient ultrasonic treatment. JU99as a multifunctionalphoto-sensitive material promises its potential application in X-ray detection.3. A multifunctional photochromic and thermochromic zeolitic material JU101has been synthesized with in-situ generated MV as the structure-directingagent. JU101exhibits a novel zeolite topology with interconnecting8×10×10channel system. JU101represents advantages as a photochromism andthermochromism material: dual photo-/thermoactivated coloration, extendedphoto-responsive range from UV to visible light, high thermal stability, and ultralong-lived charge-separated state. It also displays tuneable photovoltaicactivity coupled with the photo-/thermochromism. The successful synthesisof JU101and finding of its unusual properties associated with the MVspecies will open a new vista in searching for materials with usefulphotophysical functionalities.