Thermal Stability and Kinetics of Single I2@ZIF-8 Particles.

ABSTRACT

Thermogravimetric analysis (TGA) is a key material characterization method for studying the thermal stability and thermochemical process. However, the common TGA for bulk samples lacks sufficient spatial information, which blurs the intrinsic thermal decomposition characteristic and limits the understanding of the structure-performance relationship. Here, we report a dark-field microscope (DFM) method for studying thermal desorption process of I2 from I2-loaded zeolitic imidazolate framework-8 (I2@ZIF-8). Because of the high spatial resolution, DFM enables the imaging and tracking of the local mass loss of I2 in single I2@ZIF-8 particles at different reaction temperatures. We obtain from the DFM images the single-particle thermogravimetric and differential thermogravimetric curves to evaluate the inherent thermal stability of single I2@ZIF-8 particles. We also find the heterogeneous thermal decomposition property among different I2@ZIF-8 particles. Furthermore, we demonstrate the capacity of DFM to quantitatively determine thermal kinetics parameters such as the diffusion coefficient and activation energy of I2 in individual and multiple ZIF-8 particles. These useful results are essential for developing high-efficient porous adsorbents for the capture of I2.