Porous Organic Cages

Abstract

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.

Constructing Ultrastable Metallo-Cages via In Situ Deprotonation/Oxidation of Dynamic Supramolecular Assemblies

“…Its precision highly rests on dynamic noncovalent interactions (hydrogen bonds, π–π interactions, hydrophobic effect, etc.) and reversible covalent bonds (imine, thioester, and borate ester bonds), which reversibly connect building blocks of assembled constructs. , Among the diverse fields of self-assembly, coordination-driven self-assembly is flourishing for building up a vast variety of two-dimensional (2D) , and three-dimensional (3D) supramolecular structures, owing to the dynamic and directional features of coordination interactions as well as the wide range of available metal ions and ligands. However, the inherent reversibility of noncovalent interactions can lead to transformations or disassociation of supramolecules, when they are exposed to different environments.…”

Efficient multigram procedure for the synthesis of large hydrazone-linked molecular cages

“…With our new, more efficient procedure we were able to synthesize three new larger cages, which represent some of the largest covalent molecular tetrahedra reported to date. 39,40…”

Eutectic Molten Salt Synthesis of Highly Microporous Macrocyclic Porous Organic Polymers for CO2 Capture

“…Moreover, the abundance of micropores (< 2 nm) and ultramicropores (< 0.7 nm) is another essential factor to increase CO 2 affinity owing to the interaction of CO 2 with multiple binding sites. [13] We recently summarized [3] the most critical parameters determining the CO 2 capture capacity for POPs, which also highlights the incorporation of shape-persistent macrocycles and cages, [14] that can host guest molecules i. e., CO 2 and optimize the pore size and geometry for high CO 2 affinity into POPs. [7,15,16] The introduction of various macrocycles such as cyclodextrins, pillar [5]arenes and calix [4]arenes into the POP-backbone have been shown to optimize properties of POPs for specific applications such as the removal of pollutants, [17,18] gas adsorption and separation, [19,20] sensing and catalysis.…”