In contrast to biological cell membranes, it is still a major challenge for synthetic membranes to efficiently separate ions and small molecules due to their similar sizes in the sub-nanometer range. Inspired by biological ion channels with their unique channel wall chemistry that facilitates ion sieving by ion-channel interactions, the first free-standing, ultrathin (10–17 nm) nanomembranes composed entirely of polydopamine (PDA) are reported here as ion and molecular sieves. These nanomembranes are obtained via an easily scalable electropolymerization strategy and provide nanochannels with various amine and phenolic hydroxyl groups that offer a favorable chemical environment for ion-channel electrostatic and hydrogen bond interactions. They exhibit remarkable selectivity for monovalent ions over multivalent ions and larger species with K⁺/Mg²⁺ of ≈4.2, K⁺/[Fe(CN)₆]³⁻ of ≈10.3, and K⁺/Rhodamine B of ≈273.0 in a pressure-driven process, as well as cyclic reversible pH-responsive gating properties. Infrared spectra reveal hydrogen bond formation between hydrated multivalent ions and PDA, which prevents the transport of multivalent ions and facilitates high selectivity. Chemically rich, free-standing, and pH-responsive PDA nanomembranes with specific interaction sites are proposed as customizable high-performance sieves for a wide range of challenging separation requirements.

中文翻译：

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使用超薄聚多巴胺纳米膜进行离子和分子筛分


与生物细胞膜相比，由于离子和小分子在亚纳米范围内的尺寸相似，有效分离离子和小分子仍然是合成膜的一大挑战。受生物离子通道及其独特的通道壁化学物质的启发，该化学物质通过离子通道相互作用促进离子筛分，第一个完全由聚多巴胺（PDA）组成的独立式超薄（10-17 nm）纳米膜在此被报道为离子筛和分子筛。这些纳米膜是通过易于扩展的电聚合策略获得的，并提供具有各种胺和酚羟基的纳米通道，为离子通道静电和氢键相互作用提供了有利的化学环境。与多价离子和较大物质相比，它们对单价离子表现出显着的选择性，K ⁺ /Mg ²⁺ 为 ≈4.2，K ⁺ /[Fe(CN) < b3> ] ³⁻ 约为 10.3，K ⁺ /罗丹明 B 约为 273.0 在压力驱动过程中，以及循环可逆 pH 响应门控特性。红外光谱揭示了水合多价离子和 PDA 之间形成的氢键，这阻止了多价离子的传输并有利于高选择性。具有特定相互作用位点的化学成分丰富、独立且 pH 响应的 PDA 纳米膜被提议作为可定制的高性能筛子，满足各种具有挑战性的分离要求。