Development of Coordination Polymer Glass as a Luminescent Solar Concentrator Materials

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Porous glasses are highly sought for separation, energy and catalytic applications. However, for the existing materials fine control of pore structure and hence properties are very difficult. Coordination polymers(CPs) are designer inorganic hybrid framework materials widely studied for gas storage/separation, catalysis, magnetic, ionics applications. While crystalline CPs are prevalent in the literature the amorphous glassy states of CPs have attracted much attention due to defect rich dynamic structure and excellent formability. With careful review in the area of glassy and liquid states of CPs, we identified the key challenges need immediate attention. Controlled transfer of porous properties of crystalline CPs to glassy CPs is one of the important challenges. We have synthesized new porous CP Cu(dpp)TFSI (dpp=1,3-Di(4-pyridy)propane; TFSI=(trifluoromethanesulfonyl)imide). The CP formed a glass on melt quenching but the porosity was lost completely although the glass structure was found to be same as the crystalline one. We then utilized mechanical milling induced glass formation. The CP showed glassy behavior with sorption capacity better than the crystals. Milling time is used as tool to introduce different amounts of defects in CP glass which allowed us to precisely control the porous properties of CP glass. The shaping ability of CP glass(in the form of pellets) is found to be superior than the crystalline CP thanks to dangling and highly dynamic bonds in glasses. Reversible crystal-glass-crystal formation in milled glass is rare and is to be further investigated.