The use of covalent organic frameworks (COFs) in practical applications demands shaping them into macroscopic objects, which remains challenging. Herein, we report a simple three‐step method to ...produce COF aerogels, based on sol‐gel transition, solvent‐exchange, and supercritical CO2 drying, in which 2D imine‐based COF sheets link together to form hierarchical porous structures. The resultant COF aerogel monoliths have extremely low densities (ca. 0.02 g cm−3), high porosity (total porosity values of ca. 99 %), and mechanically behave as elastic materials under a moderate strain (<25–35 %) but become plastic under greater strain. Moreover, these COF aerogels maintain the micro‐ and meso‐porosity of their constituent COFs, and show excellent absorption capacity (e.g. toluene uptake: 32 g g−1), with high removal efficiency (ca. 99 %). The same three‐step method can be used to create functional composites of these COF aerogels with nanomaterials.
A three‐step method produces COF aerogel monoliths, based on sol–gel transition, solvent‐exchange, and supercritical CO2 drying. 2D imine‐based COF sheets link together to form hierarchical porous structures. The aerogels have extremely low densities, high porosity, and mechanically behave as elastic or plastic materials under different strain. They show excellent absorption capacity with high removal efficiency.
•Covalent Organic Frameworks timeline evolution.•Strategies of preparation of Covalent Organic Frameworks.•Developments in the processability of Covalent Organic Frameworks.•Perspectives on potential ...uses of Covalent Organic Frameworks.
Covalent Organic Frameworks are highly versatile porous materials that have attracted much attention over the last few years. This review summarizes the timeline of its development, highlighting the shifts in the targets deemed necessary to use them in real-world applications. We have collected aspects concerning COF formation and the strategies developed to gain chemical stability by using different linkages between the initial building blocks and modulating the structural characteristics of COFs. Importantly, we have also included elements concerning material processability that has been incorporated in the research field of COFs but are essential to solving many different applications of COFs. Finally, we included a summary section providing headlines of this research field to get closer to real applications.
High energy demand results in comprehensive research of novel materials for energy sources and storage applications. Covalent organic frameworks (COFs) possess appropriate features such as long‐range ...order, permanent porosity, tunable pore size, and ion diffusion pathways to be competitive electrode materials. Herein, we present a deep electrochemical study of two COF‐aerogels shaped into flexible COF‐electrodes (ECOFs) by a simple compression method to fabricate an electrochemical double‐layer capacitor (EDLC). This energy storage system has considerable interest owing to its high‐power density and long cycle life compared with batteries. Our result confirmed the outstanding behavior of ECOFs as EDLC devices with a capacity retention of almost 100 % after 10 000 charge/discharge cycles and, to our knowledge, the highest areal capacitance (9.55 mF cm−2) in aqueous electrolytes at higher scan rates (1000 mV s−1) for COFs. More importantly, the hierarchical porosity observed in the ECOFs increases ion transport, which permits a fast interface polarization (low τ0 values). The complete sheds light on using ECOFs as novel electrode material to fabricate EDLC devices.
Covalent organic framework (COFs) aerogels are shaped into flexible electrode composite by a simple compression method. It shows permanent porosity and great ion diffusion pathways appropriated for electrochemical double‐layer capacitors (EDLC). These EDLC devices demonstrated a significant areal capacitance (11.2 mF cm−2) with the lowest τ0 reported in COF‐based capacitors, 50 ms, and a 98 % capacitance retention over 10 000 charge/discharge cycles.
Demand continues for processing methods to shape covalent organic frameworks (COFs) into macroscopic objects that are needed for their practical applications. Herein, a simple compression method to ...prepare large‐scale, free‐standing homogeneous and porous imine‐based COF‐membranes with dimensions in the centimeter range and excellent mechanical properties is reported. This method entails the compression of imine‐based COF‐aerogels, which undergo a morphological change from an elastic to plastic material. The COF‐membranes fabricated upon compression show good performances for the separation of gas mixtures of industrial interest, N2/CO2 and CH4/CO2. It is believed that the new procedure paves the way to a broader range of COF‐membranes.
Large‐scale free‐standing covalent organic framework (COF)‐membranes are prepared via a simple compression method using imine‐based COF‐aerogel compression. This straightforward method produces free‐standing and homogeneous COF‐membranes with sizes in the centimeter range and excellent mechanical properties. They show good performance for gas separation of mixtures of industrial interest.
High energy demand results in comprehensive research of novel materials for energy sources and storage applications. Covalent organic frameworks (COFs) possess appropriate features such as long‐range ...order, permanent porosity, tunable pore size, and ion diffusion pathways to be competitive electrode materials. Herein, we present a deep electrochemical study of two COF‐aerogels shaped into flexible COF‐electrodes (ECOFs) by a simple compression method to fabricate an electrochemical double‐layer capacitor (EDLC). This energy storage system has considerable interest owing to its high‐power density and long cycle life compared with batteries. Our result confirmed the outstanding behavior of ECOFs as EDLC devices with a capacity retention of almost 100 % after 10 000 charge/discharge cycles and, to our knowledge, the highest areal capacitance (9.55 mF cm−2) in aqueous electrolytes at higher scan rates (1000 mV s−1) for COFs. More importantly, the hierarchical porosity observed in the ECOFs increases ion transport, which permits a fast interface polarization (low τ0 values). The complete sheds light on using ECOFs as novel electrode material to fabricate EDLC devices.
Covalent organic framework (COFs) aerogels are shaped into flexible electrode composite by a simple compression method. It shows permanent porosity and great ion diffusion pathways appropriated for electrochemical double‐layer capacitors (EDLC). These EDLC devices demonstrated a significant areal capacitance (11.2 mF cm−2) with the lowest τ0 reported in COF‐based capacitors, 50 ms, and a 98 % capacitance retention over 10 000 charge/discharge cycles.
The use of covalent organic frameworks (COFs) in practical applications demands shaping them into macroscopic objects, which remains challenging. Herein, we report a simple three‐step method to ...produce COF aerogels, based on sol‐gel transition, solvent‐exchange, and supercritical CO2 drying, in which 2D imine‐based COF sheets link together to form hierarchical porous structures. The resultant COF aerogel monoliths have extremely low densities (ca. 0.02 g cm−3), high porosity (total porosity values of ca. 99 %), and mechanically behave as elastic materials under a moderate strain (<25–35 %) but become plastic under greater strain. Moreover, these COF aerogels maintain the micro‐ and meso‐porosity of their constituent COFs, and show excellent absorption capacity (e.g. toluene uptake: 32 g g−1), with high removal efficiency (ca. 99 %). The same three‐step method can be used to create functional composites of these COF aerogels with nanomaterials.
A three‐step method produces COF aerogel monoliths, based on sol–gel transition, solvent‐exchange, and supercritical CO2 drying. 2D imine‐based COF sheets link together to form hierarchical porous structures. The aerogels have extremely low densities, high porosity, and mechanically behave as elastic or plastic materials under different strain. They show excellent absorption capacity with high removal efficiency.
The copper‐catalyzed azide–alkyne cycloaddition (CuAAC) click reaction is among the most extensively used strategies for the post‐polymerization modification of COFs. This work shows a new procedure ...for the postsynthetic functionalization of imine‐based COFs by using a heterogeneous solid–gas reaction between alkyne‐functionalized COFs and azides in the absence of a copper catalyst. This new alternative represents a step forward towards a greener postsynthetic modification of COFs opening a high potential for the development of new applications.
Click! Postsynthetic functionalization of imine‐based COFs is carried out at the solid–gas (COF–azide) interface, without solvent and catalyst, in high yield. This procedure is a green postsynthetic modification of COFs and allows for the preparation of 2D materials with high potential for the development of new applications.
Abstract Covalent organic frameworks (COFs) possess intrinsic nanoscale pores, limiting mass transport and impacting their utility in many applications, such as catalysis, supercapacitors, and gas ...storage, demanding efficient diffusion throughout the material. Hierarchical porous structures, integrating larger macropores with inherent micro‐/meso‐pores, facilitate rapid mass transport. Recently, the fabrication of aerogel monoliths is reported exclusively from imine‐linked COFs, offering flexibility in aerogel composition. However, challenges in synthesizing robust β‐ketoenamine‐based COFs with comparable surface areas prompted innovative synthetic approaches. Leveraging the dynamic nature of COF bonds, in this work efficient monomer exchange from imine to partially β‐ketoenamine‐linked COFs within the gel phase is demonstrated. These aerogels can be transformed into electrodes using the compression technique. The new flexible electrodes‐based β‐ketoenamine‐linked COF composites with C super P exhibit superior durability and redox activity. Through supercapacitor assembly, the β‐ketoenamine‐linked COF electrodes outperform their imine‐based counterparts, showcasing enhanced capacitance (88 mF cm −2 ) and stability at high current densities (2.0 mA cm −2 ). These findings underscore the promise of β‐ketoenamine‐linked COFs for pseudocapacitor energy storage applications.
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