High-performance Hf/Ti-doped defective Zr-MOFs for cefoperazone adsorption: Behavior and mechanisms

Due to the excessive use, cephalosporin antibiotics have been detected in various aquatic environments, which may result in environmental and health concern. In this study, bimetallic metal-organic frameworks (MOFs), HfUiO-66 and Ti-UiO-66, were successfully designed and obtained via post-synthetic method from UiO-66 for the adsorption of cefoperazone. A serious of adsorption experiments were investigated. The adsorption kinetics and isotherms demonstrated that the adsorption process followed pseudo-second-order kinetic model and Langmuir isotherm model. Hf/Ti-UiO-66 exhibited much better adsorption performance than the undoped UiO-66. Particularly, Hf-UiO-66 had the highest adsorption capacity (346.0 mg g-1). With the introduction of Hf or Ti, the chemical coordination environment changed, which resulted in defective structures of MOFs. Such defective structures increased the adsorption active sites, changed the surface charges and enlarged pores. Based on the characterization by FT-IR, XPS, and zeta potential, it was identified that the electrostatic attraction, pi-pi stacking, hydrogen bonding and metal complexation were the driving force for the high adsorption capacity of the bimetallic MOFs. The as-prepared MOFs displayed good stability and reusability. This work provides a great prospect for the design and application of bimetallic defective MOFs in cephalosporins removal in environmental water.

Automated summary

In this study, bimetallic metal-organic frameworks HfUiO-66 and Ti-UiO-66 were successfully designed for the adsorption of cephalosporin antibiotics. The introduction of Hf or Ti changed the chemical coordination environment of the MOFs, resulting in increased adsorption active sites, altered surface charges, and enlarged pores. The driving forces for high adsorption capacity included electrostatic attraction, pi-pi stacking, hydrogen bonding, and metal complexation.