Pore isotherms can be used, for example, to elucidate the reason for the steps observed in the total adsorption isotherms (Fig. ). The pore isotherms for DUT-32 show that all pores have a drastic increase in uptake at ≈ 4×10 -2 bar followed by another filling step for the largest pore (p3) at ≈ 1 × 10 -1 bar. This filling process is different to UMCM-1 where the initial step is associated with the smallest pores. It appears the smallest pores p1 and p2 fill together but the large pore only be- gins filling after adsorption is near saturation in the smallest pores. The two-step filling processes in the largest pore (p3) of UMCM-1 does not appear to happen alongside but instead following adsorption in the smallest pores. The cooperative nature of all or some of the pores in DUT-32 and UMCM-1 is not present in NU-1000, where each of the pores fill seemingly independently, adsorption begins in the smallest pore, then medium pore and finally the largest pore. The above pore isotherms outline three different adsorption behaviours responsible for the steps observed in the total isotherms (Fig. ). For each material the largest pore is greater than 24 Å, which would be classified as a mesopore (pore diameter > 20 Å, demonstrating the expected type-IV behaviour for a pore of this size. However, as observed for DUT-32 the surrounding pores can cooperatively fill at the same pressure leading to a departure from simple type-IV behaviour. These pore isotherms demonstrate the size of the pore does not necessarily dictate at which pressure adsorption occurs. Gas adsorption occurs at the medium sized pores in DUT-32 and UMCM-1 before the smallest pore highlighting the influence of pore structure on adsorption.