Isomerous Al-BDC-NH2 metal-organic frameworks for metronidazole removal: Effect of topology structure

Herein, three isomerous Al-BDC-NH2 metal-organic frameworks including CAU-1, CAU-6 and MIL-101-NH2 were synthesized and studied for metronidazole (MNZ) adsorption. In CAU-6, the narrow 1D channel is easily blocked and large proportion of μ-OH groups are invalid due to pore size limitation. The large window entrance of MIL-101-NH2 permits the diffusion of MNZ into the 3D cage, while the oversize access induces a large freedom degree of diffusion and thereby reduces the mass transfer efficiency. The 3D cage with suitable window size of CAU-1 results in the highest adsorption capacity (254.6 ​mg ​g-1), via the help of H-bond interaction. The adsorption of MNZ in CAU-1 reaches equilibrium at ∼360 ​min, and co-existing salts have negligible effects on the adsorption. Besides, CAU-1 can be well regenerated through a simple elution method. Thus, our work demonstrates that CAU-1 can serve as a potential adsorbent for MNZ, and 3D pore with suitable size will promote the capture of small antibiotic molecules. The 3D pore with suitable size results in the optimized adsorption of MNZ in CAU-1. [Display omitted] •Three isomerous Al-BDC-NH2 materials with similar compositions were studied for MNZ adsorption.•3D pore with suitable size proved to be the ideal topology for MNZ capture.•CAU-1 demonstrated to be a high-efficiency adsorbent for MNZ.