Copper-doping induced hierarchically porous metal-organic framework for enhanced adsorption of cefradine antibiotic

Development of hierarchically porous materials is important for adsorptive removal of antibiotic with large molecular size. Herein, we proposed a novel strategy for constructing hierarchically porous metal-organic frameworks (MOFs), via introducing low-coordination-number copper in zirconium-oxygen clusters. Compared with UiO-66 (UiO, University of Oslo), the Cu-doped sample exhibits larger specific surface area and importantly, abundant defects and large rhombus-like window. Benefited from that, cefradine is easily diffused into the cages of UiO-66. The resultant UiO-66-Cu owns much higher adsorption capacity (325.1 mg g(-1)) for this antibiotic than Cu-absence sample does (102.0 mg g(-1)), which is also superior to those reported adsorbents. Besides, adsorption equilibrium was obtained at similar to 600 min. It is found that the adsorption behavior can be well described by Langmuir isotherm model and pseudo-second-order model. The adsorption is gradually enhanced along with the increasing pH (2.0-8.0). Co-existing ions including Na+, K+, Ca2+, Mg2+, Cl-, NO3- and SO42- commonly have negligible effects on the adsorption. Finally, the adsorbent can be well regenerated by using ethanol as the eluent. Mechanism investigation indicates that cefradine adsorption in UiO-66-Cu is driven by electrostatic, hydrogen bond and coordination interactions. Thus, our work provides an effective adsorbent for cefradine and meanwhile proposes a new approach to construct hierarchically porous MOFs.

Automated summary

A novel strategy for constructing hierarchically porous metal-organic frameworks (MOFs) by introducing low-coordination-number copper in zirconium-oxygen clusters is proposed. The Cu-doped MOF exhibits larger specific surface area and higher adsorption capacity for cefradine compared to the Cu-absence sample and other reported adsorbents. The adsorption behavior is well-described by Langmuir isotherm model and pseudo-second-order model, and is gradually enhanced with increasing pH. The adsorbent can be effectively regenerated using ethanol as the eluent, and the mechanism of cefradine adsorption is driven by electrostatic, hydrogen bond and coordination interactions.