Qian Li

The surging demand for lithium in new energy storage has shifted the focus of lithium extraction from high-grade resources to low-grade brines. Low-grade brine is rich in lithium resources. However, its extraction process is quite challenging due to the severe interference from coexisting ions. Traditional extraction technologies are characterized by low selectivity and high energy consumption. In contrast, lithium-ion imprinted polymers (Li-IIPs) based on the "lock and key" recognition mechanism offer a promising alternative for the efficient recovery of lithium from low-grade brines. This review systematically summarizes the latest research achievements on Li-IIPs. It covers the preparation principles, selection criteria for raw materials, and comparative analysis of mainstream manufacturing methods. Surface imprinting technology is highlighted for its superiority in enhancing the adsorption capacity and mass transfer efficiency by mitigating imprinted site encapsulation. Moreover, a comprehensive performance evaluation system is established. It includes adsorption capacity, selectivity, kinetics, and regeneration stability, with emphasis on the regulatory effects of complex brine conditions (pH, time, temperature, and coexisting ions). The synergistic effects of Li-IIPs in combination with precipitation, membrane separation, solvent extraction, and other emerging technologies are further discussed. Finally, the current bottlenecks and future development directions are identified. Overall, this review aims to provide guidance for the advancement of Li-IIP technology and facilitate its translation from the laboratory scale to the industrial scale, thereby promoting the extraction of lithium resources from low-grade brines.

Different from the most used ionic liquids or cosolvents of the cellulose dissolution system, we reported a cellulose dissolution method by coupling LiBr·3H₂O preimpregnation at room temperature (RT) with dissolution of cellulose in formic acid (FA) for controllable production of nanocellulose. This method yields a high solubility (up to 10 wt %) of cellulose, which consequently facilitates the preparation of tunable regenerated nanocellulose formate (RNCF) with versatile applications. The LiBr·3H₂O preimpregnation at RT significantly improved the dissolution efficiency of cotton pulp by increasing cellulose accessibility via largely breaking hydrogen bonds and deconstructing the cellulose crystalline structure. This effect was attributed to the synergistic actions of hydrated Li⁺ coordination with the O of cellulose hydroxyls and the bond of Br^- to H of cellulose hydroxyls, based on the verification of XPS, solid-/liquid-state NMR, and hydrogen-deuterium exchange characterization. The subsequent FA dissolution and regeneration process yielded RNCF with 100% yield, high degree of substitution (DS > 1.2), and tunable degree of polymerization (300-700) of the resultant RNCF. The dissolved CF in FA can serve as a functional building block to reassemble as strong RNCF filaments, films, hydrogels, or aerogels via a versatile regeneration route. The nanosized RNCF is further showcased to stabilize both oil-in-water and high internal phase water-in-oil Pickering emulsions. Therefore, this simple, ambient, sustainable, and cost-effective LiBr·3H₂O preimpregnation approach could largely enhance cellulose accessibility, highly promoting cellulose dissolution and sustainable production of RNCF and boosting the utilization of cellulose-based functional materials.

High‐valent cobalt‐oxo species (Co ^IV ═O) are key intermediates in catalytic chemistry but suffer a great challenge in their efficient and mild synthesis due to the strong electronic repulsion between the cobalt center and the oxygen ligand. Herein, we report a new approach to synthesizing surface Co ^IV ═O on the Co ₃ O ₄ /BiVO ₄ (CoBi) catalyst via a photoexcited hole‐induced process using water as the oxygen atom source. The interfacial Co ²⁺ ─O─Bi ³⁺ bonds act as the atomic‐level channels to directionally transport photoexcited holes driven by the internal electric field effect. It has been found that H ₂ O was photolyzed to cobalt‐coordinated hydroxyls that were turned to Co ^IV ═O via a photoexcited hole‐induced deprotonation. The isotopic labeling experiments confirmed that the oxygen atom source of Co ^IV ═O was derived from water rather than chlorite. A synergistic effect was formed between photocatalysis and transition metal‐catalyzed chlorite activation, which enhanced the degradation of sulfadiazine (SDZ) and elevated the conversion ratio of chlorite to chlorine dioxide (ClO ₂ ) from 40% to 60%. The present work has elucidated the essential role of H ₂ O and photoexcited holes in the formation of Co ^IV ═O and provides a viable strategy to synthesize surface high‐valent metal species utilizing ubiquitous water and sunlight for water purification.