Porous organic cages (POCs) are a relatively new class of low-density crystalline materials that have emerged as a versatile platform for investigating molecular recognition, gas storage and separation, and proton conduction, with potential applications in the fields of porous liquids, highly permeable membranes, heterogeneous catalysis, and microreactors. In common with highly extended porous structures, such as metal–organic frameworks (MOFs), covalent organic frameworks (COFs), and porous organic polymers (POPs), POCs possess all of the advantages of highly specific surface areas, porosities, open pore channels, and tunable structures. In addition, they have discrete molecular structures and exhibit good to excellent solubilities in common solvents, enabling their solution dispersibility and processability─properties that are not readily available in the case of the well-established, insoluble, extended porous frameworks. Here, we present a critical review summarizing in detail recent progress and breakthroughs─especially during the past five years─of all the POCs while taking a close look at their strategic design, precise synthesis, including both irreversible bond-forming chemistry and dynamic covalent chemistry, advanced characterization, and diverse applications. We highlight representative POC examples in an attempt to gain some understanding of their structure–function relationships. We also discuss future challenges and opportunities in the design, synthesis, characterization, and application of POCs. We anticipate that this review will be useful to researchers working in this field when it comes to designing and developing new POCs with desired functions.

中文翻译：

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多孔有机笼

多孔有机笼 (POC) 是一类相对较新的低密度结晶材料，已成为研究分子识别、气体储存和分离以及质子传导的多功能平台，在多孔液体、高渗透性等领域具有潜在应用膜、多相催化和微反应器。与金属有机骨架 (MOF)、共价有机骨架 (COF) 和多孔有机聚合物 (POP) 等高度扩展的多孔结构一样，POC 具有高比表面积、孔隙率、开孔通道的所有优点和可调结构。此外，它们具有离散的分子结构，在普通溶剂中表现出良好至优异的溶解性，使它们的溶液具有可分散性和可加工性——在成熟的、不可溶的、扩展的多孔框架的情况下不容易获得的特性。在这里，我们提出了一个批判性的评论，详细总结了所有 POC 的最新进展和突破——尤其是在过去五年中——同时仔细研究了它们的战略设计、精确合成，包括不可逆键形成化学和动态共价化学、高级表征和多样化的应用。我们重点介绍具有代表性的 POC 示例，以试图了解它们的结构-功能关系。我们还讨论了未来在 POC 的设计、合成、表征和应用方面的挑战和机遇。