Multifunctional MOGs Composites For Elimination And Fluorescence Detection Of Chlortetracycline Hydrochloride: Performances And Mechanisms

Environmental contamination induced by chlortetracycline hydrochloride（CTC）has evolved into a severe issue.In terms of their adverse effects on ecosystems and human health,it is essential to explore efficient elimination and sensitive detection approaches towards CTC for environmental governance.Metal-organic gels（MOGs）feature distinctive hierarchical pore structures,excellent stabilities,tremendous specific surface areas,and multiple responsive properties,which furnish a new possibility for the design of multifunctional materials.In this case,based on the selection of metal centers and the introduction of magnetic components,this research devised and constituted a series of functional MOGs with efficient elimination and sensitive fluorescence detection performances,which holds promise for the integrated"detection and elimination"of CTC.Beyond these,the functional MOGs were immobilized in sodium alginate（SA）to achieve the construction of macrostructure MOGs/SA to solve the issues of untoward reclamation and potential secondary pollution of powdered MOGs.The main research contents are as follows:First of all,bifunctional luminescent MOGs based on luminescent metal centers Tb³⁺and Eu³⁺（denoted as Tb-MOG and Eu-MOG）were fabricated by an ultrafast room-temperature method.In terms of adsorption,Tb-MOG and Eu-MOG exhibited exceptional adsorption capacities(297.68 mg·g^–1 and 258.78 mg·g^–1)towards CTC,and the underlying adsorption mechanisms were considered to be the combined contribution of pore filling,water affinity,hydrogen bonding interaction,π-πinteraction,and electrostatic interaction.Meanwhile,in terms of fluorescence detection,Tb-MOG and Eu-MOG possessed high sensitivities(1.48×10⁶ M^–1 and 1.12×10⁶ M^–1),and low detection limits（0.044μM and 0.057μM）towards CTC,and the inner filter effect（IFE）mechanism was responsible for the fluorescence quenching of MOGs.Further to that,luminescent MOGs/SA were constructed by immobilizing MOGs into the SA matrix.On the one hand,luminescent MOGs/SA realized continuous treatment and visual fluorescence detection of CTC in various water samples.Subsequently,considering that the adsorption could not achieve the destruction of CTC structures and the separation abilities of powdered MOGs need to be further improved,bifunctional magnetic MOGs（Fe₃O₄/Fe-MOG and Fe₃O₄/Al-MOG）with hierarchical porous structures and visible light response abilities were synthesized through the ultrafast room-temperature synthesis of MOGs with catalytic metal centers of Fe³⁺and Al³⁺on the surface of Fe₃O₄–COOH.Under visible light irradiation,Fe₃O₄/MOGs owned exceptional adsorption-photocatalysis abilities（94.3%and 90.2%,40 min）towards CTC,along with favorable magnetic separation capabilities.Synchronously,the adsorption-photocatalysis synergistic mechanisms were accomplished by the formation of reactive oxygen species（h⁺and·O₂^–）to react with adsorbed CTC,which effectively regenerated the adsorption sites of Fe₃O₄/MOGs that were occupied by multiple adsorption interactions.More importantly,magnetic MOGs/SA were developed with SA as the backbone and magnetic MOGs as the reaction center,which achieved long-term continuous operation for CTC degradation in various water samples under visible light irradiation.Ultimately,the optimization metal centers(Tb³⁺and Fe³⁺)in luminescent MOGs and magnetic MOGs were determined to construct a multifunctional magnetic luminescent Fe Tb-MOG（Fe₃O₄/Fe Tb-MOG）to realize the removal and detection of CTC.Under the synergistic effect of adsorption-photocatalytic,Fe₃O₄/Fe Tb-MOG realized exceptional adsorption-photocatalysis ability towards high-concentration CTC（95.0%,40 min）and trace CTC（91.5%,5 min）,along with favorable magnetic separation capability.Moreover,the synergistic mechanism of adsorption-photocatalysis was verified,and the probable degradation pathway of CTC was deduced.Simultaneously,in terms of fluorescence detection,Fe₃O₄/Fe Tb-MOG presented high sensitivity(1.43×10⁶ M^–1)and low detection limit（0.088μM）towards CTC,and the existence of the IFE mechanism was confirmed.On top of that,the immobilized Fe₃O₄/Fe Tb-MOG/SA not only realized long-term continuous operation for CTC elimination in the adsorption-photocatalytic reactor,but also enabled the visualization and real-time quantitative detection of CTC concentration in various water samples with the help of smartphones.In general,this research successfully constructed a series of functional MOGs through the facile and green preparation methods,and provided a rational design of MOGs based on sodium alginate carriers.One can envisage that this research might furnish valuable insights into the detection and elimination of the practical tetracycline antibiotics wastewater issues represented by CTC.