Covalent Organic Frameworks for the Capture, Fixation, or Reduction of CO2

Abstract

Covalent organic frameworks (COFs) are porous crystalline organic polymers which have been the subject of immense research interest in the past 10 years. COF materials are synthesized by the covalent linkage of organic molecules bonded in a repeating fashion to form a porous crystal that is ideal for gas adsorption and storage. Chemists have strategically designed COFs for the purpose of heterogeneous catalysis of gaseous reactants. Presented in this critical review are efforts toward developing COFs for the sequestration of CO 2 from the atmosphere. Researchers have determined the CO 2 adsorption capabilities of several COFs is competitive with the highest surface area materials. Engineering the pore environment of COFs with chemical moieties that interact with CO 2 have increased the CO 2 adsorption performance. The installation of CO 2 binding moieties in the COF has made possible the selective adsorption of CO 2 over other gases such as N 2 . The high degree of control of internal pore composition in COFs is coupled with high CO 2 adsorption to develop heterogeneous catalysts for the conversion of CO 2 to value added products. Two notable examples of this catalysis are the fixation of CO 2 to epoxides for the synthesis of cyclic carbonates and the reduction of CO 2 to CO. Recent examples of COFs for the capture of CO 2 will be discussed followed by COF catalysts which use CO 2 as a feedstock for the production of value-added products.

3D Cage COFs: A Dynamic Three-Dimensional Covalent Organic Framework with High-Connectivity Organic Cage Nodes

“…To support this, 3D-CageCOF-1 has a maximum CO 2 uptake of 204 mg g –1 at 273 K and 1 bar, and 107 mg g –1 at 298 K and 1 bar ( Figure 4 a), which are among the highest values reported for COFs under these conditions ( Figure S20 ). 49 − 51 3D-CageCOF-1 also exhibits an S-shaped water vapor sorption isotherm with a small desorption hysteresis at 298 K, which is a desirable sorption behavior for water capture by nanoporous solids. 52 In addition, 3D-CageCOF-1 shows a steep pore filling in the pressure ( P / P 0 ) range of 0.21–0.34, achieving an adsorption capacity of 22 wt % at P / P 0 = 0.4 and a maximum capacity of 33 wt % ( Figure 4 b); this is comparable with the best performing COF material (COF-432) reported for water harvesting.…”

A Carbocationic Triarylmethane‐Based Porous Covalent Organic Network

“…Extended covalent organic networks [6, 7] (CON) and correlated systems, on the other hand, are nanoporous solids, which have been used as catalysts, [8, 9] gas capture, [10] adsorption, [11–13] optoelectricity, [14–16] and energy storage [17–19] . It would be interesting to build CONs from inexpensive functional building blocks, such as the commercially available triarylmethane dyes.…”

“…These compounds have been explored in many high-tech applications, including devices such as lasers, organic light-emitting diodes (OLEDs), liquid crystal displays (LC), opticald ata storage, [2,4] and eventually been used in the formation of stable polymeric networks. [5] Extended covalent organic networks [6,7] (CON) and correlated systems, on the other hand, are nanoporous solids,w hich have been used as catalysts, [8,9] gas capture, [10] adsorption, [11][12][13] optoelectricity, [14][15][16] and energy storage. [17][18][19] It would be interesting to build CONs from inexpensive functional building blocks, such as the commerciallya vailable triarylmethane dyes.…”

Metal–organic frameworks for carbon dioxide capture

“…128,129 Organic-(F, 130,131 141 Furthermore, phosphonate groups can be applied as high polar groups in MOFs for strong interaction with quadrupolar guests like CO 2 . 19,142,143 In ether-based MOFs, the flexibility and polarity of -C-O-Cmoiety leads to a selective CO 2 capture. 144 SNU-21H and SNU-21S, containing the flexible H 4 TCM, show selective and reversible CO 2 adsorption over N 2 gas at room temperature.…”