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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 °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.

The present study established a time-saving technique for hydrogen uptake measurements using a high-pressure thermo-gravimetric analyzer (HPTGA). The critical buoyancy effects were considered in the analysis model. The HPTGA technique developed here for metal–organic frameworks (MOFs) was validated through independent experiments. The room temperature (RT) hydrogen uptake of MOFs via spillover was significantly enhanced by use of a bridge-building treatment. MOF samples with different structural parameters and RT hydrogen uptake performance can be prepared and manipulated through various factors affecting their synthesis. The structural evolution of MOFs within various steps during the synthesis and bridge-building processes were investigated by electron microscopy, nitrogen sorption isotherm analysis, and powder X-ray diffraction.

The metal-organic frameworks (MOF) with low and medium specific surface areas (SSA) were shown to be able to adsorb hydrogen via bridged spillover at room temperature (RT) up to an amount of full coverage of hydrogen in the MOF. Anomalous small-angle X-ray scattering was employed to investigate the key relationship between the structures and storage properties of the involved materials. It was found that the tunable imperfect lattice defects and the 3D pore network in the MOF crystal are the most critical structures for RT hydrogen uptake rather than the known micropores in the crystal, SSA, and Pt catalyst structure.