Abstract：
Two-dimensional polymers (2DPs) and their layer-stacked 2D covalent organic frameworks (2D COFs) membranes hold great potential for harvesting sustainable osmotic energy. The nascent research has yet to simultaneously achieve high ionic flux and selectivity, primarily due to inefficient ion transport dynamics. This is directly related to ultrasmall pore size (<3 nm), much smaller than the duple Debye length in the diluted electrolyte (6~20 nm), as well as low charge density (<4.5 mC m-2). Here, we introduce a π-conjugated viologen-based 2DP (V2DP) membrane possessing a large pore size of 4.5 nm, strategically enhancing the overlapping of the electric double layer, coupled with an exceptional positive surface charge density (~6 mC m-2). These characteristics enable the membrane to facilitate high anion flux while maintaining ideal selectivity. Notably, V2DP membranes realize an impressive current density of 5.5×103 A m-2, surpassing previously nanofluidic membranes. In practical application scenario involving the mixing of artificial seawater and river water, the V2DP membranes exhibit a considerable ion transference number of 0.70 towards Cl-, contributing to an outstanding power density of ~55 W m-2. Theoretical calculations reveal that the large quantity of anion transport sites act as binding sites evenly located in the positively charged N-containing pyridine rings.
摘要：
二维聚合物（2DP）及其层叠的2D共价有机框架（2DCOF）膜具有获取可持续渗透能的巨大潜力。新生的研究尚未同时实现高离子通量和选择性,主要是由于低效的离子传输动力学。这与超小孔径（<3nm）直接相关，远小于稀释电解质中的双德拜长度（6〜20nm），以及低电荷密度（<4.5mCm-2）。这里,我们介绍了一种基于π共轭紫精的2DP（V2DP）膜，该膜具有4.5nm的大孔径，战略性地加强双电层的重叠，加上特殊的正表面电荷密度(~6mCm-2)。这些特性使膜能够促进高阴离子通量,同时保持理想的选择性。值得注意的是,V2DP膜实现了令人印象深刻的5.5×103Am-2的电流密度，超过了以前的纳米流体膜。在涉及人工海水和河水混合的实际应用场景中，V2DP膜表现出相当大的离子向Cl-转移数0.70，为〜55Wm-2的出色功率密度做出贡献。理论计算表明，大量的阴离子转运位点作为均匀位于带正电荷的含N吡啶环中的结合位点。
