Structure Evolution of Chemically Degraded ZIF‑8

Exposure
of the metal–organic zeolitic imidazolate framework-8
(ZIF-8) to humid SOx gas cleaves Zn–N
bonds, leading to framework disorder and a corresponding decrease
in pore accessibility. This work shows that framework disorder exhibits
a critical behavior with respect to water concentration in the gas
stream. While the quantity of sulfate adsorbed at Zn nodes is at or
below the detection threshold for the X-ray pair distribution function
technique, precluding direct observation of the adsorbate, powder
diffraction reveals clear structural alterations. The onset of linker
cleavage correlates to a large microstrain that diminishes as framework
disorder increases. Energy-dispersive X-ray spectroscopy shows that
the sulfur distribution throughout representative grains is uniform,
implying the structure transformation is homogeneously nucleated and
not dependent upon gas diffusion kinetics.