Flexibility induced high-performance MOF-based adsorbent for nitroimidazole antibiotics capture

Efficient capture of nitroimidazole antibiotics from wastewater remains a serious task for public health and environmental protection. In this report, we first propose a strategy of using highly flexible metal-organic framework for dimetridazole (DMZ) capture and excellent performance was achieved. Remarkably, MIL-53(Al) exhibits an excellent saturated adsorption capacity of 467.3 mg g(-1), surpassing all previous reported MOF-based adsorbents and various adsorbent materials like active carbons. Besides, it also shows extremely fast adsorption rate at the initial concentration of 40 mg L-1. Over 90% of DMZ can be removed within 10 min and the adsorption kinetics will reach equilibrium after 60 min of contact. Moreover, the concrete interaction mechanism between DMZ and MIL-53(Al) was also investigated. The PXRD results show that MIL-53(Al) presents its narrow pore (NP) form in low DMZ concentration. Due to the overlap of potential energy, the van der waals interaction between DMZ and the framework of MIL-53(Al) can be significantly reinforced, leading to strong host-guest interaction and thereby excellent DMZ removal efficiency. As DMZ concentration increasing, the pore structure of MIL-53(Al) was propped open and switched to large pore (LP) form, further promoting its uptake capacity. This flexible adsorbent shows obvious advantage with higher removal efficiency and uptake capacity as compared with its rigid analogical adsorbents of MIL-68(Al) and Al-1,4-NDC. Our work therefore presents an effective adsorbent material for DMZ capture and this strategy of using flexible adsorbents may provide a new perspective for removing other nitroimidazole antibiotics from contaminated water for environmental remediation.