microporevolume

Micropore volume is the volume of pores with widths below 2 nanometers in a porous solid. It is a key descriptor of microporous materials such as activated carbons, zeolites, metal–organic frameworks, and porous polymers. The micropore volume is usually denoted V_micro and reported in cubic centimeters per gram (cm3/g) of material, and may be given as a fraction of the total pore volume.

Micropore volume is typically determined from gas adsorption isotherms. Common probe molecules are nitrogen at 77 K and carbon dioxide at 273 K. Microporosity can be quantified by methods such as the t-plot, which separates micropores from the external surface, or by model-based approaches using non-local density functional theory (NLDFT) or quenched solid DLVO (QSDFT) kernels to derive pore-size distributions and cumulative micropore volume.

In practice, V_micro reflects the accessible pore space for small adsorbates. CO2 adsorption at 273 K is often more sensitive to narrower micropores than N2 at 77 K, and reported micropore volumes can differ depending on the probe molecule and model employed.

Relation to performance: micropore volume correlates with adsorption capacity for gases and vapors, particularly at low relative pressures, and is a major factor in storage and separation applications. It complements mesopore and macropore volumes, which dominate capacity and kinetics at higher relative pressures.