Removal of phenazopyridine as a pharmacological contaminant using nanoporous metal/covalent-organic frameworks (MOF/COF) adsorbent

Abstract This study is aimed at employing the Molecular Dynamics simulations to assess the phenazopyridine (PHP) adsorption, an analgesic drug, on three new metal-organic frameworks (MOFs); IRMOF-16, HKUST-1, and ZIF-8, with excellent behavior in π−π stacking, H-bonding, and electrostatic interactions. To further decipher the adsorption mechanism of PHP on MOFs, coarse-grained (CG) simulations and density functional theory (DFT) calculations were also exploited. Simulations revealed the PHP adsorption intensity of around 100%, 60%, and 40% by IRMOF-16, HKUST-1, and ZIF-8, respectively. Moreover, CG simulations and DFT calculation validated the superior PHP adsorption capacity of IRMOF-16 with the energy value of -343.4 kJ/mol and -1.53 eV, respectively. Furthermore, the PHP adsorption capability of IRMOF-16 was scrutinized under three distinct modifications: functionalization with hydroxyl functional group, tuning porosity size, and hybrid framework formation with DAAQ-TFP Covalent Organic Frame (COF). Interestingly, the modification of IRMOF-16 with hydroxyl groups and grafting with the COF led to considerably better performance in removing PHP, since their modifications increased the negative net charge of the surface, resulting in greater interactions with the positively charged PHP molecules. Furthermore, enlarging the IRMOF-16 pore size relatively reduced the adsorption functionality, due to the limited interactions of PHPs with available active sites.