<p>The titanium-based ion sieve H₂TiO₃ (HTO) is recognized for its high lithium adsorption capacity and exceptional structural stability, making it a leading candidate for lithium extraction from aqueous resources. In this study, chromium-doped H₂TiO₃ (HCTO) was synthesized via a high-temperature solid-state method to enhance lithium adsorption performance. A series of characterization techniques were employed to analyze HCTO’s structure, morphology, specific surface area, and valence state evolution. Static adsorption experiments were performed to evaluate HCTO’s adsorption performance and elucidate its mechanism. Experimental results and density functional theory (DFT) calculations demonstrate that Cr³⁺ doping induces oxygen vacancies (Ovs) formation in the HTO lattice, reduces Li⁺ diffusion barriers in the solid phase, enhances electron transport efficiency, and strengthens electrostatic Li⁺-adsorbent interactions, collectively improving Li⁺ adsorption performance. Cr³⁺ incorporation effectively mitigates particle agglomeration, resulting in HCTO’s specific surface area reaching 46.04&#xa0;m²&#xa0;g⁻¹. Additionally, the crystal defects induced by Cr³⁺ doping create a “pinning effect”, thereby enhancing the structural stability of the adsorbent material. Experimental data demonstrate that HCTO-1% achieves a Li⁺ adsorption capacity of 48.07&#xa0;mg&#xa0;g⁻¹ in lithium-containing solutions, representing a 61.58% enhancement compared to unmodified HTO. After five adsorption–desorption cycles, the Ti⁴⁺ dissolution rate in HCTO-1% remained below 0.20%, demonstrating excellent cycling stability. In salt lake brine, HCTO-1% exhibits high Li⁺ selectivity over competing cations. Mechanistic studies reveal that the adsorption process of Li⁺ on HCTO-1% follows an ion exchange mechanism, involving the breaking of O–H bonds and the formation of O–Li bonds.</p> Graphical Abstract <p></p>