Mesoporous Metal-Organic Framework MIL-101 at High Pressure

Area of Science:

• Materials Science
• Chemistry
• Nanotechnology

Background:

• Chromium terephthalate MIL-101 is a mesoporous metal-organic framework (MOF) known for high adsorption capacity due to its large pores.
• External pressure can alter MOF structures and their interactions with guest molecules.

Purpose of the Study:

• To investigate the structural and vibrational behavior of MIL-101 under varying pressure conditions.
• To explore the influence of different pressure-transmitting media (PTMs) on MIL-101's stability and guest molecule interactions.

Main Methods:

• Synchrotron X-ray diffraction was used to analyze structural changes under pressure.
• Infrared (IR) spectroscopy probed the vibrational properties, particularly hydroxyl (OH) group behavior.
• Experiments utilized solid (NaCl) and fluid (Nujol, silicone oil) PTMs.

Main Results:

• Solid PTMs (NaCl) induced irreversible amorphization of MIL-101 at ~0.4 GPa.
• Fluid PTMs (Nujol, silicone oil) caused minor lattice expansion and altered OH vibrations below 0.1 GPa.
• Framework stability significantly increased, with amorphization onset shifted to ~7 GPa when using fluid PTMs, indicating fluid insertion into pores.

Conclusions:

• Fluid insertion into MIL-101 pores is confirmed by structural and spectroscopic data under pressure.
• The presence of guest fluids profoundly affects the host-guest interactions and framework stability.
• High pressure facilitates the incorporation of large polymers into mesoporous MOFs, demonstrated by silicone oil insertion below 0.2 GPa.