A series of bio-compatible zeolitic imidazolate frameworks (ZIF-7, ZIF-8 and ZIF-9) have been studied as potential carriers for drug delivery applications. Grand canonical Monte Carlo (GCMC) simulations were performed to study the adsorption of three anti-cancer drugs namely 5-Fluorouracil, Hydroxyurea and Mercaptopurine. Adsorption isotherms, snapshots and energy of adsorption were used to analyze the drug delivery process. Our GCMC simulations revealed the high capacities of studied ZIFs (0.65e0.68 g/g) for the adsorption of 5-Fluorouracil and Hydroxyurea. ZIF-8 showed high capacity (0.55 g/g) for the adsorption of Mercaptopurine, while the adsorption capacity of ZIF-7 and ZIF-9 for Mercaptopurine were moderate (about 0.36e0.44 g/g). The high heat of adsorption (115e133 kJ/mol for 5-Fluorouracil in ZIF-8 and 200e240 kJ/mol for Mercaptopurine in three ZIFs) also suggests a controlled release process. The analysis of snapshots and radial distribution functions (RDFs) showed that the adsorption of drugs occurred preferentially in the 6-membered pores of ZIFs.
