Molecular Probing in a Metal-Organic Framework for Selective Gas Adsorption and Separation

Area of Science:

• Materials Science
• Chemistry
• Nanotechnology

Background:

• Metal-organic frameworks (MOFs) show promise for selective gas adsorption and separation.
• Understanding atomic-level host-guest interactions in nanosized MOFs is crucial for rationalizing separation preferences but remains experimentally challenging.

Purpose of the Study:

• To develop a molecular probing strategy combined with cryo-3D electron diffraction (ED) to elucidate host-guest interactions and cooperative binding sites in MOFs.
• To rationalize the gas separation capabilities of MOFs at the atomic level.

Main Methods:

• Utilized a molecular probing strategy with carefully selected gas molecules (CO2, Xe) to map binding domains within a candidate MOF (SU-100).
• Employed cryo-3D electron diffraction (ED) for atomic-level structural analysis of host-guest interactions.
• Identified van der Waals forces, coordination bonds, and dipole-dipole interactions, as well as cooperative dual open metal sites.

Main Results:

• The molecular probing and cryo-3D ED approach successfully mapped multiple host-guest interactions in SU-100.
• Discovered additional adsorption sites involving cooperative dual open metal sites, facilitating the adsorption of molecules with a specific electronic configuration (Bδ−-Aδ+−Bδ−).
• Demonstrated SU-100's remarkable performance for SO2 adsorption, including high uptake, excellent stability, and effective removal of trace SO2 in the presence of CO2 and N2.

Conclusions:

• The combined molecular probing and cryo-3D ED strategy is effective for revealing atomic-level interactions and cooperative binding sites in MOFs.
• This approach enables rationalization of MOF separation preferences and guides the design for targeted gas adsorption and separation applications.
• The studied MOF (SU-100) exhibits significant potential for industrial applications, particularly in flue gas desulfurization during CO2 capture and recycling.