Covalent Organic Frameworks: The Rising‐Star Platforms for the Design of CO₂ Separation Membranes

Abstract

Membrane‐based carbon dioxide (CO2) capture and separation technologies have aroused great interest in industry and academia due to their great potential to combat current global warming, reduce energy consumption in chemical separation of raw materials, and achieve carbon neutrality. The emerging covalent organic frameworks (COFs) composed of organic linkers via reversible covalent bonds are a class of porous crystalline polymers with regular and extended structures. The inherent structure and customizable organic linkers give COFs high and permanent porosity, short transport channel, tunable functionality, and excellent stability, thereby enabling them rising‐star alternatives for developing advanced CO2 separation membranes. Therefore, the promising research areas ranging from development of COF membranes to their separation applications have emerged. Herein, this review first introduces the main advantages of COFs as the state‐of‐the‐art membranes in CO2 separation, including tunable pore size, modifiable surfaces property, adjustable surface charge, excellent stability. Then, the preparation approaches of COF‐based membranes are systematically summarized, including in situ growth, layer‐by‐layer stacking, blending, and interface engineering. Subsequently, the key advances of COF‐based membranes in separating various CO2 mixed gases, such as CO2/CH4, CO2/H2, CO2/N2, and CO2/He, are comprehensively discussed. Finally, the current issues and further research expectations in this field are proposed.

Application of Metal/Covalent Organic Frameworks in Separators for Metal‐Ion Batteries

“…Rational selection of organic linkers and introduction of additional hydrogen bonding among frameworks can effectively improve MOFs and COFs' stability. [56] For example, Banerjee et al first reported the ketoenamine-linked COFs with high chemical stability owing to the irreversible nature of the whole reaction without an imine bond. [57] An easy way to measure the chemical stability of separators is by observing the corrosion resistance and the rate of expansion and contraction after soaking in the liquid electrolyte for some time.…”

Expanding the horizons of covalent organic frameworks: sub-stoichiometric synthesis as an emerging toolkit for functional COFs

“…49–52 The field has also witnessed the utilization of unreacted sites, the introduction of non-interfering functional groups, and post-synthetic modifications that functionalize the pores or transform the linkages. 30,33,53 The functional versatility of such framework materials has led to various applications, including gas adsorption/separation, 54–57 host–guest chemistry, 58–61 sensing, 62–68 ion capture/transport, 69 catalysis, 70–76 and electrochemical applications. 77…”

“…[49][50][51][52] The eld has also witnessed the utilization of unreacted sites, the introduction of noninterfering functional groups, and post-synthetic modications that functionalize the pores or transform the linkages. 30,33,53 The functional versatility of such framework materials has led to various applications, including gas adsorption/separation, [54][55][56][57] host-guest chemistry, 58-61 sensing, [62][63][64][65][66][67][68] ion capture/transport, 69 catalysis, [70][71][72][73][74][75][76] and electrochemical applications. 77 Focussed research activities on COFs that started with the rst report via the formation of dynamic boroxine and boronate ester bonds have now been extended to seeded growth of 2D COFs, graphene nanoribbon 2D COFs, and recently to water harvesting frameworks.…”

Low-Resistance Transport Pathways in POSS/CPBI Mixed Matrix Membranes for Efficient CO2 Separation

“…Biogas is one of the most readily available and widespread renewable energies, and it is usually obtained from the decomposition of biodegradable waste. − Biogas has been expected to replace the conventional fossil fuel . However, CO 2 in biogas not only causes corrosion of equipment and pipelines but also greatly reduces the calorific value of biogas. − Hence, it is required to take CO 2 out of biogas.…”