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) 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 electrochemical double‐layer capacitors (EDLCs) are highly demanded electrical energy storage devices due to their high power density with thousands of cycle life compared with pseudocapacitors and batteries. Herein, a series of capacitor cells composed of exfoliated mesoporous 2D covalent organic frameworks (e‐COFs) that are able to perform excellent double‐layer charge storage is reported. The selected mesoporous 2D COFs possess eclipsed AA layer‐stacking mode with 3.4 nm square‐like open channels, favorable BET surface areas (up to 1170 m2 g−1), and high thermal and chemical stabilities. The COFs via the facile, scalable, and mild chemical exfoliation method are further exfoliated to produce thin‐layer structure with average thickness of about 22 nm. The e‐COF‐based capacitor cells achieve high areal capacitance (5.46 mF cm−2 at 1,000 mV s−1), high gravimetric power (55 kW kg−1), and relatively low τ0 value (121 ms). More importantly, they perform nearly an ideal DL charge storage at high charge–discharge rate (up to 30 000 mV s−1) and maintain almost 100% capacitance stability even after 10 000 cycles. This study thus provides insights into the potential utilization of COF materials for EDLCs.

have been employed as promising electrochemical double-layer capacitor (EDLC) electrodes [34] and electrical conductors. [35] In the field of batteries, electrocatalysis, and fuel cells, COFs have also appeared recently. [36-38] In this review article, the recent progress in the design and synthesis of electroactive COFs and their applications in the fields of electrochemical energy storages (EES), electrochemical energy conversions and electrocatalysis are overviewed. Their performances as capacitor, battery, conductor, fuel cell, and electrocatalysis are discussed. Furthermore, the perspectives on developing electroactive COFs as future smart materials for energy storage and conversion are provided. 2. Design Principles of Electroactive COFs To enable COFs to conduct both ions and electrical charges or store electrochemical energy in capacitors and batteries requires the specific design of electroactive sites within the structure. Similarly, to execute electrocatalytic phenomena in the key electrochemical reactions (e.g., ORR, OER, and HER), COF-based electrocatalysts should possess catalytic sites that are able to undertake efficient catalytic processes and avoid overpotential. [39] Thus, careful design of electroactive COFs with abundant accessible active sites, long-term durability, and if possible, low-cost and greener technologies is pivotal. The design of electroactive COFs has been performed in various strategies. These strategies include preparing COFs with high surface areas and accessible active surfaces, incorporating electroactive sites (e.g., electron-rich species and metals) in their frameworks, and hybridizing COFs with other electroactive components to enhance their electroactivity. To make these more practical, we provide a scheme (Scheme 1) to describe how electroactive COFs were designed so far and further discuss them in the following subsections. 2.1. Electroactive Bulk and Exfoliated COFs The accessible surface areas and active sites in porous materials influence their activities. Therefore, bulk and exfoliated COFs have been prepared to improve the accessibility toward their electroactive sites (Scheme 1a). COFs have been widely prepared as bulk crystalline powder and employed in various applications. [40-43] Meanwhile, efforts in the development of bulk COFs with controlled pore size and to drive for more accessibility of the active sites were reported. For example, Jiang and co-workers prepared a high-surface-area mesoporous 2D imide-linked D TP-A NDI-COF with a pore size of 5.06 nm for the construction of Li-ion battery electrode. [44] Li and co-workers reported another 2D imide-linked PIBN-based COF with a pore size of 1.4 nm for a similar application. [45] These two electroactive COFs with distinct porosity exhibited remarkable and unique performances in the field of battery. In addition, COFs have also been prepared as bulk thin films or membranes. For example, Halder et al. synthesized flexible, self-standing, and chemically stable thick sheet (≈200 µm) TpOMe-DAQ film (where TpOMe ...