Kinetic restrictions in the characterization of narrow microporosity in carbon materials

Textural characterization of porous solids is commonly carried out by N-2 adsorption at 77 K. Additionally, CO2 adsorption at 273 K and sub-atmospheric pressure was proposed as a complement to N2 for the more complete characterization of the narrow microporosity. However, and contrary to the general assumption, CO2 adsorption may be kinetically restricted in narrow pores (< 0.3-0.4 nm), in spite of the high-temperature (273 K) at which the measurement is carried out, thus giving rise to an erroneous characterization.