The increasing global demand for lithium, driven by its central role in energy storage and clean-energy technologies, necessitates the development of more efficient and sustainable recovery methods. Conventional extraction techniques from salt-lake brines are resource-intensive and have a significant environmental impact, motivating the need for advanced materials capable of selective lithium capture under mild conditions.

This work explores the design of CO₂-responsive polymer networks incorporating crown ether motifs for selective and reversible lithium binding. The central hypothesis is that 12-crown-4 ether units, functionalized with tertiary amines and embedded within a crosslinked polymer matrix, can provide size-selective coordination of Li⁺ while enabling external control over ion adsorption and desorption through CO₂-triggered changes in the polymer microenvironment.

Statistical copolymers are synthesized via RAFT polymerization, combining ion-binding crown ether units, hydrophobic components for structural stability, and crosslinking sites to form networks. Upon CO₂ exposure, protonation of tertiary amines increases network charge density and hydrophilicity, leading to swelling that disrupts Li⁺ coordination and enables controlled ion release. Through systematic variation of polymer composition, this study evaluates the relationships between structure, stimulus response, and ion sorption performance. Quantitative adsorption and desorption studies assess lithium uptake, reversibility, and selectivity in the presence of competing ions (Mg²⁺, Na⁺, K⁺).

Overall, this research establishes a molecular design framework for adaptive, stimuli-responsive sorbent materials, offering a promising strategy for selective lithium recovery from complex aqueous systems while contributing to the advancement of next-generation responsive materials.