Highly selective capture of lead(II) by a barium-zinc-antimony-oxo cluster-based material: Ion-exchange pathway with single-crystal-to-single-crystal structural transformation.

Highly selective capture of Pb2+ is achieved by an barium-zinc-antimony-oxo cluster-based material in the presence of an excess of individual or multiple competing ions. The mechanism of the capturing and desorbing of Pb2+ ions is unveiled from the perspective of structural chemistry for the first time, that is, the ion exchange between Pb2+ and Ba2+ ions. [Display omitted] • A highly stable cluster-based material FJSM-BZA for lead remediation. • FJSM-BZA exhibits fast kinetic response and excellent selectivity for Pb2+. • Unprecedented SC-SC transformation during Pb2+ adsorption and elution. • Pb2+ capture mechanism illuminated at the molecular level for the first time. Efficient removal of Pb2+ from wastewater is of great significance for human health and environmental protection. However, Pb2+ capture from complex wastewater is still very challenging due to the strong competition with other metal ions. Herein, the highly selective removal of Pb2+ has been achieved by a cluster-based material, namely H 1.03 Ba 2.485 (H 2 O) 15 [Zn 2 Sb 12 (μ 3 -O) 8 (μ 4 -O) 3 (tta) 6 ]·8H 2 O (H 4 tta = tartaric acid) (FJSM-BZA). FJSM-BZA exhibits high adsorption capacity (199.29 ± 5.86 mg/g) and fast kinetic response (kinetic equilibrium is reached in 20 min) for Pb2+. In particular, even in the presence of competing ions Mn2+, Co2+, Ni2+, Cu2+, and Cd2+, FJSM-BZA maintains excellent selectivity for Pb2+ with removal rate much higher than that of other metal ions. The material after Pb2+ adsorption could be regenerated by a simple elution method. The unprecedented single-crystal-to-single-crystal (SC to SC) structural transformations during Pb2+ adsorption and elution are unveiled, which helps directly elucidate the distinctive mechanisms of ion exchange between Ba2+ and Pb2+. It is revealed that the strong coordination interactions of the active carboxyl groups at the periphery of the cluster with Pb2+ ions are the intrinsic driving forces for the ion-exchange. This work highlights the design and synthesis of crystalline metal-oxo cluster-based materials for highly selective removal of Pb2+. [ABSTRACT FROM AUTHOR]