<p>We report on the design and performance of composite sorbents based on 4',4''(5'')-di-<i>tert</i>-butyldicyclohexano-18-crown-6 and novel fluorinated diluents for the selective separation and pre-concentration of ²¹⁰Pb and ²¹⁰Po. The sorbents were synthesized by impregnation of a solid support with solutions of the crown ether in three fluorinated diluents: 3-nitrobenzotrifluoride (F-3), bis(2,2,3,3-tetrafluoropropyl) carbonate (BK-1), and bis(2,2,3,3-tetrafluoropropoxy)-methane (FN-1). The synthesis was optimized with respect to the choice of support, solvent, and key conditions—namely, impregnation temperature and time, as well as crown ether concentration. Optimal performance was achieved using a styrene–divinylbenzene support (LPS-500, 50–60&#xa0;μm) impregnated with 1&#xa0;mol L^–1 crown ether solution in the diluent, using chloroform as a solvent which was subsequently removed. The materials were comprehensively characterized by IR spectroscopy, XPS, SEM, and EDS. These analyses confirmed the successful incorporation of active components into the support. Among the studied diluents, BK-1 provided the highest lead distribution coefficients, reaching up to (8.6 ± 0.6)·10³&#xa0;mL&#xa0;g^–1. Efficient recovery of ²¹⁰Pb and ²¹⁰Po from 1&#xa0;mol L^–1 HNO₃ was achieved with distribution coefficients values up to 7.05·10³ and 2.93·10³&#xa0;mL&#xa0;g^–1, respectively, and quantitative desorption was accomplished using 5–6&#xa0;mol L^–1 HCl. This combination of high distribution coefficients, pronounced selectivity in acidic media, and facile regeneration using HCl solutions demonstrates the potential of these novel composites for practical application in the separation and preconcentration of lead, including radionuclides ²¹⁰Pb and ²¹⁰Po, from complex matrices.</p>