Adsorption of Ar on each of the materials was simulated using grand canonical Monte Carlo (GCMC) simulations as employed by the YAFF package (version 1.6.0.post21). To produce representative isotherms simulations were performed for 75 values of gas pressure and the chemical potential at each temperature and gas pressure was calculated with the Peng-Robinson equation of state. Monte Carlo steps of insertion, deletion and translation were used in equal probability and 1 × 10 7 steps were simulated and the final 5 × 10 6 steps used to compute the average properties. Interactions were treated by the Lenard-Jones potential: