Construction of Charge Transfer Complexes for Highly Selective Detection and Ultraefficient Separation of Uranium

Selective detection and efficient separation of uranium from lanthanides (Ln) is very important but currently remains a great challenge considering the chemical similarities between uranium and Ln. Herein, a charge transfer complex (CTC) (TPP-TCNQ CTC) was constructed by introducing triphenylphosphine (TPP) as the donor and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as the receptor. The optical properties of TPP-TCNQ CTC, including absorption, fluorescence, and light scattering (LS), simultaneously exhibit distinct evolution upon the specific interaction with UO₂²⁺, facilitating its sensitive and selective detection with the limit of detection (LOD) down to 6.7 nM for the LS method. More importantly, TPP-TCNQ CTC can coordinate with UO₂²⁺ to form coprecipitation in a wide pH range (1.0-9.0) with fast kinetics (1 min) and high specificity (K_d^U, 3.48 × 10⁴ mL g^-1), achieving the efficient precipitation separation of UO₂²⁺ (>90%) without complex procedures. The specific coprecipitation of UO₂²⁺ over other Ln favors highly selective detection and ultraefficient separation of UO₂²⁺ and endows the TPP-TCNQ CTC with great potential in rare earth tailings treatment. This work offers a new strategy for charge transfer complex (CTC) construction and a promising platform for the detection and separation of radioactive nuclides.