Figure 4. Differential pore size distributions calculated from N2 isotherms using the 2D-NLDFT up to 2 nm (A) and cumulative pore volume (B).
This increase in the level of defects should be reflected in an increased porosity. The nitrogen adsorption isotherms and the pore size distributions calculated from them [33] are presented in Figures 3 and 4, respectively. The addition of nGr increased the volume of N2 adsorbed, and the calculated surface areas of the composites increased by about 30 % compared to that of UiO-66 (Table 1). This increase in the surface area is consistent with the decrease in the numbers of linkers per node discussed above. Interestingly, no trend in the porosity development was found with an increase in the nGr content, and the S BET of all composites remained at the level of about 1600 m2/g. The volumes of ultra-, micro-, mesopores and the total pore volumes of the composites are also higher than those of UiO-66.
Table 1. Textural parameters calculated from N2adsorption isotherms at – 196°C.