This review highlights the state-of-the-art progress achieved in two-dimensional covalent organic frameworks (COFs) with hierarchical porosity, an emerging class of COFs constructed by integrating different types of pores into one framework.

New linkage chemistry will endow covalent organic frameworks (COFs) with not only structural diversity but also fascinating properties. However, to develop a new type of linkages has been a great challenge. We herein report the first two COFs using aminal as the linkages. These two COFs have been synthesized by condensation of secondary amine and aldehyde. They crystallize in cpi net, which is a new topology for COFs. The aminal linkage is found to favor reservation of photophysical property of the monomers due to its tetrahedral geometry and nonconjugated feature. These aminal-COFs exhibit good thermal stability and high chemical stability under neutral and basic conditions.

A gaseous hydrogen chloride chemosensor has been developed based on a 2D covalent organic framework (COF), which exhibits a very fast response and high sensitivity to gaseous HCl through distinct changes in fluorescence emission and color.

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Solution-phase self-assembly of two-dimensional (2D) networks with a high degree of internal order and long-range periodicity is a great challenge. Herein, we report a rational design to improve 2D self-assembly in water through amphiphilic modification of the building block. An amphiphilic tritopic molecule ( 1) is designed and synthesized by introducing three hydrophilic oligo(ethylene glycol) moieties and three hydrophobic hexyl chains. The assembly of 1 and cucurbit [8]uril (CB[8]) leads to the formation of a Janus 2D supramolecular organic framework (SOF), which further creates unique bilayer supramolecular networks and exhibits an unprecedentedly high degree of internal order and long-range periodicity. In contrast, the assembly of a nonamphiphilic analog (2) with CB[8] only generates a 2D SOF with a lower degree of internal order, suggesting that the inherent amphiphilicity of 1 plays a crucial role in improving its 2D self-assembly in aqueous phase.

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Boron‐based covalent organic frameworks (COFs) are susceptible to nucleophilic attack by water at the electron‐deficient boron sites and even slightly humid air could destroy the integrity of their porous frameworks within hours. Such instability is a major limitation to the practical applications of boron‐based COFs. Herein we report a significant enhancement of hydrostability of boroxine‐linked COFs (COF‐1 as representative) by modification with an oligoamine (tetraethylenepentamine, TEPA), which leads to survival of the modified COF in water and long‐time stability under humid atmosphere. Meanwhile, the TEPA modification also results in a considerable increase in CO2 adsorption capacity up to 13 times and a dramatic improvement in CO2/N2 selectivity in low pressure region, which make the modified COF suitable for capturing CO2 from flue gas. This work provides a facile, efficient, and scalable method to greatly improve hydrostability of boroxine‐linked COFs and reshape them into high‐performance CO2 adsorbents.

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