A New Pore Shape Analysis Method Based on the Adsorption-Controlled ¹²⁹Xe-NMR Technique

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Determining pore shapes in crystalline materials is established, but challenging for amorphous nanoporous materials.
• Previous work validated adsorption-controlled 129Xe-NMR for pore size evaluation in slit-shaped porous carbons.

Purpose of the Study:

• To investigate the potential of adsorption-controlled 129Xe-NMR for pore shape analysis in amorphous nanoporous materials.
• To differentiate pore shapes (slit vs. cylindrical) and analyze pore connectivity using 129Xe-NMR.

Main Methods:

• Utilized adsorption-controlled 129Xe-NMR spectroscopy on diverse carbon- and silica-based nanoporous materials.
• Analyzed pore characteristics using the pore volume to specific surface area ratio (V/SSA) and its inverse (SSA/V).
• Correlated 129Xe-NMR data with pore geometry and solid-fluid interactions via Lennard-Jones calculations.

Main Results:

• Distinct δS-SSA/V plots distinguished between cylindrical and slit-shaped nanoporous materials.
• Cylindrical pores showed higher δS values than slit-shaped pores at equivalent pore sizes, indicating stronger interactions.
• δS-V/SSA plots revealed distinct correlations for different material series, reflecting pore connectivity gradients.

Conclusions:

• Adsorption-controlled 129Xe-NMR is a promising technique for analyzing pore shape in amorphous nanoporous materials.
• The method effectively assesses pore size, shape, and connectivity across various nanoporous material types.
• This advancement offers new possibilities for characterizing complex nanomaterials.