Although metal-organic frameworks offer a new platform for developing versatile sorption materials,yet coordinating the functionality,structure and component of these materials remains a great challenge.It depends on a comprehensive knowledge of a"real sorption mechanism".Herein,a ternary mechanism for U(Ⅵ)uptake in metal-organic frameworks was reported.Analogous MIL-100s(Al,Fe,Cr)were prepared and studied for their ability to sequestrate U(Ⅵ)from aqueous solutions.As a result,MIL-100(Al)performed the best among the tested materials,and MIL-100(Cr)performed the worst.The nuclear magnetic resonance technique combined with energy-dispersive X-ray spectroscopy and zeta potential measurement reveal that U(Ⅵ)uptake in the three metal-organic frameworks involves different mechanisms.Specifically,hydrated uranyl ions form outer-sphere complexes in the surface of MIL-100s(Al,Fe)by exchanging with hydrogen ions of terminal hydroxyl groups(Al-OH2,Fe-OH2),and/or,hydrated uranyl ions are bound directly to Al(Ⅲ)center in MIL-100(Al)through a strong inner-sphere coordination.For MIL-100(Cr),however,the U(Ⅵ)uptake is attributed to electrostatic attraction.Besides,the sorption mechanism is also pH and ionic strength dependent.The present study suggests that changing metal center of metal-organic frameworks and sorption conditions alters sorption mechanism,which helps to construct effective metal-organic frameworks-based sorbents for water purification.

Xiyuan Bu;Ming Tian;Hongqing Wang;Lin Wang;Liyong Yuan;Weiqun Shi

Laboratory of Nuclear Energy Chemistry,Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 100049,China;School of Chemistry and Chemical Engineering,University of South China,Hengyang 421001,China

化学科学与工程前沿

[1]Xiyuan Bu;Ming Tian;Hongqing Wang;Lin Wang;Liyong Yuan;Weiqun Shi-.A ternary mechanism for the facilitated transfer of metal ions onto metal-organic frameworks:implications for the"versatility"of these materials as solid sorbents)[J].化学科学与工程前沿,2022(11):1632-1642

sequestrate

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