Breathing porous liquids based on responsive metal-organic framework particles

Area of Science:

• Materials Science
• Chemical Engineering
• Nanotechnology

Background:

• Responsive metal-organic frameworks (MOFs) show promise for energy applications due to their structural transformations and sigmoidal gas sorption isotherms.
• Challenges exist in their application due to lack of transportability in continuous flow systems.
• Existing systems often rely on liquid agents, necessitating the development of liquid-based responsive materials.

Purpose of the Study:

• To develop responsive liquid systems exhibiting "breathing" behavior and step-shaped gas sorption isotherms.
• To create stable porous liquids from flexible MOF nanocrystals dispersed in silicone oil.
• To demonstrate gated gas uptake for CO2, propane, and propylene.

Main Methods:

• Dispersing flexible MOF nanocrystals in size-excluded silicone oil to form stable porous liquids.
• Characterizing gas sorption properties using sigmoidal isotherms with distinct transition steps.
• Utilizing in situ X-ray diffraction to investigate the structural transformations of MOF nanocrystals.

Main Results:

• Stable porous liquids were formed, exhibiting gated uptake for CO2, propane, and propylene.
• Sigmoidal gas sorption isotherms with distinct transition steps were observed, similar to haemoglobin's oxygen saturation curve.
• In situ X-ray diffraction confirmed pressure-induced narrow-to-large pore phase transformations in MOF nanocrystals within the liquid dispersion.

Conclusions:

• The development of "breathing" porous liquids opens new avenues for tunable gas sorption materials.
• These materials offer potential for energy-related applications requiring controlled gas uptake and release.
• The MOF nanocrystal dispersions in silicone oil provide a transportable and adaptable platform for responsive materials.