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

In this work, a simple metal-organic framework (MOF) material, UiO-66-NH ₂, was prepared for the highly efficient separation of artemisinin (Art) and artesunate (Aru). Selective adsorption tests showed that UiO-66-NH ₂ presented a much higher selectivity toward Aru than Art (α _Aru/Art = 40.74). The N ₂ adsorption-desorption isotherm results of UiO-66-NH ₂ indicated a suitable pore size to enable the free entry of Art and Aru. Contact angle analysis indicated that UiO-66-NH ₂ is hydrophilic with the -NH ₂ group, and can interact with the hydrophobic Aru through hydrogen bonding between the -NH ₂ and -COOH groups, which is not possible with the hydrophobic Art. The selective adsorption of Aru onto UiO-66-NH ₂ 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-NH ₂. The adsorption amount (65.24 mg g ⁻¹) and selectivity factor (α _Aru/Art = 40.74) of UiO-66-NH ₂ 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-NH ₂ provide evidence supporting the potential of MOF adsorbents for the separation of various analogous molecules.