Growth of MOF@COF on corncob as effective adsorbent for enhancing adsorption of sulfonamides and its mechanism

Abstract

MOF@COF composite was fabricated for greater adsorption capacity through the utilization of corncob, which is a natural, sustainable, and cellulose-rich resource. An in-situ growth strategy was implemented to graft UiO-66-NH2 on carboxyl-terminal corncob induced by the thermal esterification of critic acid. Subsequently, corncob@UiO-66-NH2@TpBD was constructed through the Schiff base reaction between 2,4,6-triformylphloroglucinol (Tp) and UiO-66-NH2 as well as benzidine (BD). The ratio of UiO-66-NH2 and TpBD was optimized to be 5:3 for enhancing adsorption capacity. Based on the π-π, hydrogen bonding, and -SO2-Zr-O- coordination effect, sulphonamides (SAs) were chosen to investigate the adsorption capacity of adsorbent using an in-syringe solid phase extraction (IS-SPE) method. The binding energy calculated using density functional theory (DFT) reached −37.45 Kcal/mol, which indicated the strong interactions between SAs and corncob@UiO-66-NH2@TpBD. Combined with ultra-performance liquid chromatography (UPLC), a high sensitivity was obtained with low detection of 0.10 μg/L. The prepared corncob@UiO-66-NH2@TpBD exhibited good reproducibility within relative standard deviations (RSDs) 3.1%-3.4% in intra-batch and 4.3%-8.4% in inter-batch. Moreover, the extraction capacity of adsorbent was not decreased in 20 recycles adsorption–desorption within RSDs 3.8%-8.5%. With features of permanent porosity, multiple active sites, and good renewability, corncob@UiO-66-NH2@TpBD shows great potential towards industrial applications in the field of adsorption.