Singapore Membrane Technology Center, Nanyang Environment and Water Research Institute, Nanyang Technological University, 637141, Singapore.
School of Civil and Environmental Engineering, Nanyang Technological University, 639798, Singapore.
Chem Soc Rev. 2022 Jun 6;51(11):4537-4582. doi: 10.1039/d1cs01061a.
Water channels are one of the key pillars driving the development of next-generation desalination and water treatment membranes. Over the past two decades, the rise of nanotechnology has brought together an abundance of multifunctional nanochannels that are poised to reinvent separation membranes with performances exceeding those of state-of-the-art polymeric membranes within the water-energy nexus. Today, these water nanochannels can be broadly categorized into biological, biomimetic and synthetic, owing to their different natures, physicochemical properties and methods for membrane nanoarchitectonics. Furthermore, against the backdrop of different separation mechanisms, different types of nanochannel exhibit unique merits and limitations, which determine their usability and suitability for different membrane designs. Herein, this review outlines the progress of a comprehensive amount of nanochannels, which include aquaporins, pillar[5]arenes, I-quartets, different types of nanotubes and their porins, graphene-based materials, metal- and covalent-organic frameworks, porous organic cages, MoS, and MXenes, offering a comparative glimpse into where their potential lies. First, we map out the background by looking into the evolution of nanochannels over the years, before discussing their latest developments by focusing on the key physicochemical and intrinsic transport properties of these channels from the chemistry standpoint. Next, we put into perspective the fabrication methods that can nanoarchitecture water channels into high-performance nanochannel-enabled membranes, focusing especially on the distinct differences of each type of nanochannel and how they can be leveraged to unlock the as-promised high water transport potential in current mainstream membrane designs. Lastly, we critically evaluate recent findings to provide a holistic qualitative assessment of the nanochannels with respect to the attributes that are most strongly valued in membrane engineering, before discussing upcoming challenges to share our perspectives with researchers for pathing future directions in this coming of age of water channels.
水通道是推动下一代海水淡化和水处理膜发展的关键支柱之一。在过去的二十年中，纳米技术的兴起汇集了大量多功能纳米通道，有望通过超越水-能源关系中最先进的聚合物膜的性能来重塑分离膜。如今，这些水纳米通道可以根据其不同的性质、物理化学性质和膜纳米结构的方法大致分为生物、仿生和合成三种类型。此外，在不同分离机制的背景下，不同类型的纳米通道表现出独特的优点和局限性，这决定了它们在不同膜设计中的可用性和适用性。本文综述了大量纳米通道的进展，包括水通道蛋白、[5]柱状芳烃、I-四联体、不同类型的纳米管及其孔蛋白、基于石墨烯的材料、金属和共价有机骨架、多孔有机笼、MoS 和 MXenes，为它们的潜力提供了一个比较性的视角。首先，我们从化学角度出发，通过探讨纳米通道多年来的发展历程，为背景图绘制了一个蓝图，然后讨论了它们的最新发展，重点介绍了这些通道的关键物理化学和内在传输特性。接下来，我们从实际角度出发，介绍了可以将纳米通道构建成高性能纳米通道增强膜的制造方法，特别关注每种类型的纳米通道的独特差异以及如何利用这些差异来释放当前主流膜设计中承诺的高水传输潜力。最后，我们批判性地评估了最近的发现，根据膜工程中最看重的属性对纳米通道进行了全面的定性评估，然后讨论了未来的挑战，以便与研究人员分享我们对水通道时代的未来方向的看法。
