ZIF-8 templated mesoporous triazine covalent-organic polymer for adsorptive removal of sulfonamides from water

A highly porous covalent-organic polymer with mesoporosity (named MT-MCTP) was prepared for the first time via ZIF-8 (a zeolitic imidazolate framework, comprised of ZnN4 tetrahedral units interconnected by methyl imidazolate linkers) templated synthesis of microporous triazine polymer (MCTP) and subsequent removal of ZIF-8. MT-MCTP had higher porosity and wider pore size than the conventional MCTP. The prepared MT-MCTP, together with MCTP and commercial activated carbon (AC), was applied to the adsorptive elimination of sulfonamides like sulfamethoxazole and sulfachlorpyridazine from water. MT-MCTP showed the highest kinetic constants among the three adsorbents in the sulfonamides adsorption because of the developed mesopores obtained with the sacrificial ZIF-8 template. Additionally, the adsorbed amounts of sulfamethoxazole and sulfachlorpyridazine over the adsorbents decreased in the order: MT-MCTP > MCTP > AC. MT-MCTP had a maximum adsorption capacity (Q0) of 557 and 534 mg/g for sulfamethoxazole and sulfachlorpyridazine, respectively, which are much higher than the capacity observed with AC. Importantly, MT-MCTP is a recyclable adsorbent with the highest Q0 for sulfamethoxazole compared with any reported results, so far, in near-neutral conditions. Based on the adsorption and surface charge under wide pH ranges, the noticeable sulfamethoxazole adsorption over MT-MCTP could be interpreted with the favorable pore structure (mesopore), surface charge, pi-pi interaction, and hydrogen bonding interaction.