Structural Analysis and Thermal Behavior of Pore Networks in High-Surface-Area Metal-Organic Framework

Metal-organic framework-5 (MOF-5) with high surface area was synthesized in this study. The complete picture of pore structure in the crystal from the locally perfect micropore channels to the global mesopore network distributed along the constituent micrograins was revealed by small-angle X-ray scattering (SAXS). The in situ SAXS measurement was conducted to investigate the concurrent evolution of mesopore structure and micrograin boundary during heating and thermal activation at 200 degrees C. During the pore evacuation and formation of micrograin boundary, the flexible mesopores shrink, swell, and realign, while the micropores remain stably rigid. The result shows the role of the tunable mesopore network in the MOF-5 crystal governing the migration of gas molecules. This new finding will be useful for guiding the rational crystal design and the synthetic modification for improving the crystal quality in potential applications.