An ultrastable MOF (Metal-Organic Framework), PCN-128 (PCN stands for Porous Coordination Network), was constructed from [Zr6(μ3-OH)8(OH)8]8+ node and a tetratopic linker which poccesses piezofluorochromic behavior unpon exterior stimulation. Under solvothermal reaction condition, PCN-128 was obtained as white crystalline powder. Interestingly, the color of PCN-128 was changed to yellow if exterior stimuli, including both chemical and physical treatments, were applied. Structures of both phases (PCN-128W stands for the white form, PCN-128Y stands for the yellow form) were refined against their powder x-ray diffaction pattarns. Which revealed that the change of color is resulted from the transformation of linker. What's more, as synthesized PCN-128W has a strong emission around 470 nm upon excitation at 355 nm. However, after the color change, the emission was red shifted to 535 nm under the same conditions. It was also noticed that the color change process is reversible, PCN-128Y can be converted back to PCN-128W if it was treated with TFA (trifluoroacetic acid) at elevated temperatures. Nitrogen adsorption isotherm has revealed that the BET surface area for PCN-128 is 2530 m2/g. Moreover, the crystallinity and porosity remain undestroyed during the transformation which were evidenced by powder X-ray diffraction and nitrogen adsorption isotherms respectively. The shifts of emission and the changes of pore size distribution corresponding to different stimuli will also be discussed.

Ultrastable piezofluorochromic metal-organic frameworks

249th National Meeting (2015)

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