UiO-66-NH2 as a novel ultrahigh-selective adsorbent superior to molecularly imprinted polymers for the adsorption of artesunate

Abstract

In this work, a simple metal-organic framework (MOF) material, UiO-66-NH2, was prepared for the highly efficient separation of artemisinin (Art) and artesunate (Aru). Selective adsorption tests showed that UiO-66-NH2 presented a much higher selectivity toward Aru than Art (αAru/Art = 40.74). The N2 adsorption-desorption isotherm results of UiO-66-NH2 indicated a suitable pore size to enable the free entry of Art and Aru. Contact angle analysis indicated that UiO-66-NH2 is hydrophilic with the -NH2 group, and can interact with the hydrophobic Aru through hydrogen bonding between the -NH2 and -COOH groups, which is not possible with the hydrophobic Art. The selective adsorption of Aru onto UiO-66-NH2 may be attributed to three factors: pore size, functional groups, and difference in hydrophobic/hydrophilic characteristics between the adsorbent and adsorbate. Molecularly imprinted polymers (MIPs) were prepared using Aru as a template for selective adsorption experiments to verify the excellent selectivity of UiO-66-NH2. The adsorption amount (65.24 mg g−1) and selectivity factor (αAru/Art = 40.74) of UiO-66-NH2 toward Aru were significantly better than those of the MIPs (2.039 mg g−1 and 3.072, respectively). The binding capacity and better selectivity of UiO-66-NH2 provide evidence supporting the potential of MOF adsorbents for the separation of various analogous molecules.