We summarize in this review the current state-of-the-art development of three dimensional covalent organic frameworks.

The development of crystalline porous materials (CPMs) with high chemical stability is of paramount importance for their practical uses. Here we report the synthesis of novel polyarylether covalent organic frameworks (PAE-COFs) with high crystallinity, porosity and exceptional chemical stability due to the inert nature of polyarylether building blocks. We demonstrate that these materials can be stable against harsh chemical environments involving boiling water, strong acids/bases, oxidation and reduction conditions, which exceed all known CPMs, including zeolites, metal-organic frameworks (MOFs) and COFs. Furthermore, we explore their advantages as an efficient platform for structural design and functional evolution. The functionalized PAE-COFs combine porosity, high stability, and recyclability, and deliver outstanding performance in the removal of antibiotics from water over a wide pH range.

Covalent organic frameworks (COFs) are an emerging class of porous crystalline polymers with wide range of potential applications. However, the availability of three-dimensional (3D) COFs is still limited, and their synthesis is confined to the high-temperature solvothermal method. Here, we report for the first time a general and simple strategy to produce a series of 3D ionic liquid (IL)-containing COFs (3D-IL-COFs) by using IL as a green solvent. The syntheses are carried out at ambient temperature and pressure accompanied by a high reaction speed (e.g., only three mins for 3D-IL-COF-1), and the IL can be reused without activity loss. Furthermore, the 3D-IL-COFs show impressive performance in the separation of CO/N and CO/CH. This research thus presents a potential pathway to green large-scale industrial production of COFs.

Chemical functionalization of covalent organic frameworks (COFs) is critical for tuning their properties and broadening their potential applications. However, the introduction of functional groups, especially to three-dimensional (3D) COFs, still remains largely unexplored. Reported here is a general strategy for generating a 3D carboxy-functionalized COF through postsynthetic modification of a hydroxy-functionalized COF, and for the first time exploration of the 3D carboxy-functionalized COF in the selective extraction of lanthanide ions. The obtained COF shows high crystallinity, good chemical stability, and large specific surface area. Furthermore, the carboxy-functionalized COF displays high metal loading capacities together with excellent adsorption selectivity for Nd over Sr and Fe as confirmed by the Langmuir adsorption isotherms and ideal adsorbed solution theory (IAST) calculations. This study not only provides a strategy for versatile functionalization of 3D COFs, but also opens a way to their use in environmentally related applications.

Covalent organic frameworks (COFs) are an emerging class of porous crystalline polymers with broad potential applications. So far, the availability of three-dimensional (3D) COFs is limited and more importantly only one type of covalent bond has been successful used for 3D COF materials. Here, we report a new synthetic strategy based on dual linkages that leads to 3D COFs. The obtained 3D COFs show high specific surface areas and large gas uptake capacities, which makes them the top COF material for gas uptake. Furthermore, we demonstrate that the new 3D COFs comprise both acidic and basic sites, and act as excellent bifunctional catalysts for one-pot cascade reactions. The new synthetic strategy provides not only a general and versatile approach to synthesize 3D COFs with sophisticated structures but also expands the potential applications of this promising class of porous materials.

Covalent organic frameworks (COFs) have emerged as functional materials for various potential applications. However, the availability of three-dimensional (3D) COFs is still limited, and nearly all of them exhibit neutral porous skeletons. Here we report a general strategy to design porous positively charged 3D ionic COFs by incorporation of cationic monomers in the framework. The obtained 3D COFs are built of 3-fold interpenetrated diamond net and show impressive surface area and CO uptakes. The ion-exchange ability of 3D ionic COFs has been highlighted by reversible removal of nuclear waste model ions and excellent size-selective capture for anionic pollutants. This research thereby provides a new perspective to explore 3D COFs as a versatile type of ion-exchange materials.

The functionalization of three-dimensional (3D) covalent organic frameworks (COFs) is essential to broaden their applications. However, the introduction of organic groups with electroactive abilities into 3D COFs is still very limited. Herein we report the first case of 3D tetrathiafulvalene-based COFs (3D-TTF-COFs) with non- or 2-fold interpenetrated pts topology and tunable electrochemical activity. The obtained COFs show high crystallinity, permanent porosity, and large specific surface area (up to 3000 m2/g). Furthermore, these TTF-based COFs are redox active to form organic salts that exhibit tunable electric conductivity (as high as 1.4 × 10–2 S cm–1 at 120 °C) by iodine doping. These results open a way toward designing 3D electroactive COF materials and promote their applications in molecular electronics and energy storage.

The development of three-dimensional (3D) functionalized covalent organic frameworks (COFs) is of critical importance for expanding their potential applications. However, the introduction of functional groups in 3D COFs remains largely unexplored. Herein we report the first example of 3D Salphenbased COFs (3D-Salphen-COFs) and their metal-containing counterparts (3D-M-Salphen-COFs), the later being further used as catalytic antioxidants. These Salphen-based COFs exhibit high crystallinity and specific surface area in addition to excel lent chemical stability. Furthermore, the Cu(II)-Salphen COF displayed high activity in the removal of superoxide radicals. This study not only presents a new pathway to construct 3D functionalized COFs, but also promotes their applications in biology and medicine.