Post-Synthetic Modification Unlocks a 2D-to-3D Switch in MOF Breathing Response: A Single-Crystal-Diffraction Mapping...

Area of Science:

• Materials Science
• Crystallography
• Chemistry

Background:

• Metal-organic frameworks (MOFs) exhibit dynamic behaviors like breathing upon guest molecule exchange.
• Interpenetrated diamondoid MOFs offer unique structural properties for functional applications.
• Post-synthetic modification (PSM) allows for tuning MOF properties without altering the core framework.

Purpose of the Study:

• To investigate the impact of PSM on the breathing dynamics of the interpenetrated diamondoid MOF, SHF-61.
• To characterize the structural changes and breathing mechanisms of the modified MOF, SHF-62.
• To explore the decoupling of pore-width and pore-length breathing motions.

Main Methods:

• Single-crystal-to-single-crystal post-synthetic modification (PSM) was employed.
• The modified MOF (SHF-62) was synthesized from SHF-61 via quantitative amidation.
• A series of single-crystal X-ray diffraction studies were performed to map the breathing motions.

Main Results:

• PSM of SHF-61 to SHF-62 proceeded quantitatively in a single-crystal manner.
• The breathing behavior was retained but shifted from predominantly 2D to distinctly 3D.
• Pore closing induced ring-flipping to avoid steric hindrance, decoupling pore-width and pore-length breathing.

Conclusions:

• Post-synthetic modification can effectively tune the dimensionality of breathing motions in MOFs.
• The observed 3D breathing in SHF-62 offers new possibilities for MOF-based separation and sensing applications.
• Decoupling of pore-width and pore-length breathing provides a novel mechanism for controlling guest diffusion.