Abstract
Zeolitic imidazolate frameworks (ZIFs) are very useful as high-capacity iodine (I2) adsorbents. The adsorption performance is usually probed by measuring a statistical average property over an entire sample consisting of a large number of ZIF particles, leaving the interparticle heterogeneity information among individuals. Here we report a dark-field microscopy (DFM) method to visualize gaseous I2 adsorption on single ZIF-90 particles in situ and in real time. The adsorption of I2 is found to alter the scattering spectrum of ZIF-90 particles, inducing a distinct color change from bluewhite to yellow. According to correlating the adsorption amount of gaseous I2 with the change of B value from DFM images, we quantitatively image the adsorption process and estimate the related kinetic parameters at the single particle level. Single particle measurements clarify the large particle-to-particle heterogeneity in adsorption reactivity and significant adsorption activity improvement of ZIF-90 after introduction of linker defects, which provides a microscopic understanding of the structure-activity relationship. We further demonstrate the capacity of this strategy for studying gaseous I2 adsorption on single ZIF-91 particle as a derivative of ZIF-90 to illustrate the generality.
Highlights
Zeolitic imidazolate frameworks (ZIFs) are very useful as high-capacity iodine (I2) adsorbents
To image the gaseous I2 on single ZIF-90 particles, we dropcast the ZIF-90 dispersion on a microchamber, and the gaseous I2 is pumped
In conclusion, we have demonstrated that the dark-field microscopy (DFM) method allows the visualization of gaseous I2 adsorption on single ZIF-90 particles
Summary
Zeolitic imidazolate frameworks (ZIFs) are very useful as high-capacity iodine (I2) adsorbents. We report a dark-field microscopy (DFM) method to visualize gaseous I2 adsorption on single ZIF-90 particles in situ and in real time. We investigate the dynamic of the gaseous I2 adsorption on single ZIF-90 particles in situ and in real time with dark-field microscopy (DFM) (Fig. 1), a simple and powerful tool that can image individual nanoparticles with both high resolution and high contrast. Upon the introduction of gaseous I2, the B component of the DFM image of single ZIF-90 particles significantly decreases This process accompanies distinct change in color and scattering peak, which enables and facilitates visual readout of the capture process of gaseous I2 by single ZIF-90 particle. We will show that the introduction of more defects will greatly enhance the adsorption rate and amount of gaseous I2 on single ZIF-90 particles This method is appropriate for studying other ZIF particles such. These findings offer singleparticle visualization and mechanistic understanding of defectpromoted I2 adsorption in ZIF-90, proving the efficient avenue for revealing the structure-adsorption performance relationship
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