我国锂资源需求逐年增长, 其储量主要集中于盐湖卤水中, 然而, 传统提锂技术存在能耗高、选择性低等问题. 金属有机框架(Metal-Organic Framework, MOF)凭借其可设计的亚纳米通道, 在盐湖提锂领域展现出巨大潜力. 但分散的MOFs颗粒在制膜的过程中仍存在易团聚、加工难度大、易产生晶间缺陷严重影响分离性能. 本研究采用晶种诱导原位生长策略, 在基底表面构建出连续无缺陷的MOF离子筛分膜. 本研究首先合成纳米氧化锌(ZnO)颗粒, 将其作为金属源均匀分布在聚偏二氟乙烯(PVDF)基底表面. 随后通过水热法在PVDF基底上原位生长ZIF-90选择层, 并采用旋涂工艺对MOF层晶间缺陷进行快速修复, 最终成功制备出无缺陷的ZIF-90复合膜. 性能测试表明, 该膜在锂镁离子分离过程中表现出优异的分离性能(S_Li⁺_/Mg²⁺=20), 锂离子的渗透速率高达0.225 mol•h⁻¹•m⁻²; 通过模拟计算证明了复合膜的选择性源于ZIF-90通道对Mg²⁺更高的结合能(－6.5 eV), 抑制Mg²⁺的传输. 本研究提出的快速修复膜缺陷策略, 为制备高性能的离子筛分膜提供了新思路, 对推动盐湖卤水中锂资源的高效分离与回收利用具有重要的理论参考和实际应用价值.

The demand for lithium resources in China has been increasing year by year, and their reserves are mainly concentrated in the brine of salt lakes. However, traditional lithium extraction technologies have problems such as high energy consumption and low selectivity. Metal-organic frameworks (MOFs) have shown great potential in the field of lithium extraction from salt lakes due to their designable sub-nanometer channels. However, the dispersed MOFs particles still tend to agglomerate during the membrane-making process, which makes processing difficult and prone to intergranular defects, seriously affecting the separation performance. In this study, a seed-induced in-situ growth strategy was adopted to construct a continuous and defect-free MOFs membrane on the substrate surface. Firstly, Nano zinc oxide (ZnO) particles were synthesized and uniformly distributed on the surface of polyvinylidene fluoride (PVDF) substrates as metal sources. Subsequently, the ZIF-90 selective layer was grown in situ on the PVDF substrate by the hydrothermal method, and the intergranular defects of the MOFs layer were rapidly repaired by the spin coating process. Finally, the defect-free ZIF-90 composite membrane was successfully prepared. ZIF-90 composite membrane exhibits excellent separation performance in the process of separating lithium and magnesium ions (S_Li⁺_/Mg²⁺=20), with a lithium-ion permeation as high as 0.225 mol•h⁻¹•m⁻². Simulation calculations verified that the selectivity of the composite membrane is attributed to the higher binding energy (－6.5 eV) of ZIF-90 channels toward Mg²⁺, which inhibits Mg²⁺ transport. Characterization confirmed the successful synthesis of ZIF-90. The synthesized composite membrane exhibits suitable pore sizes in ZIF-90, enabling precise separation of lithium and magnesium ions despite their small size difference. This study further investigated the effects of epoxy dosage towards ion selectivity. The optimal selectivity between monovalent and divalent ions was achieved with a certain dosage. Temperature-dependent experiments revealed that an increase in temperature led to enhanced ion flux but reduced selectivity. The activation energies for the transport of K⁺, Na⁺, Li⁺, and Mg²⁺ through the composite membrane, as derived from Arrhenius equation fitting, followed the order: E_Mg>E_Li>E_Na>E_K. The rapid membrane defect repair strategy proposed in this study provides a new idea for the preparation of high-performance ion-screening membranes and has important theoretical refer- ence and practical application value for promoting the efficient separation and recovery of lithium resources in salt lake brine.