Abstract
Removing sulfur dioxide (SO2) from exhaust flue gases of fossil fuel power plants is an important issue given the toxicity of SO2 and subsequent environmental problems. To address this issue, we successfully developed a new series of imide-linked covalent organic frameworks (COFs) that have high mesoporosity with large surface areas to support gas flowing through channels; furthermore, we incorporated 4-[(dimethylamino)methyl]aniline (DMMA) as the modulator to the imide-linked COF. We observed that the functionalized COFs serving as SO2 adsorbents exhibit outstanding molar SO2 sorption capacity, i.e., PI-COF-m10 record 6.30 mmol SO2 g−1 (40 wt%). To our knowledge, it is firstly reported COF as SO2 sorbent to date. We also observed that the adsorbed SO2 is completely desorbed in a short time period with remarkable reversibility. These results suggest that channel-wall functional engineering could be a facile and powerful strategy for developing mesoporous COFs for high-performance reproducible gas storage and separation.
Highlights
A number of technologies for fuel-gas desulfurization (FGD) have been developed using techniques such as lime scrubbing, ammonia scrubbing, and physical absorption via organic solvents, the disadvantages of these processes are prohibitive, including low efficiency and generation of huge amounts of inorganic salts, wastewater, and organic solvents[5,6,7,8]
Imide-linked covalent organic frameworks (COFs) were synthesized as a result of the co-condensation reactions of tris(4-aminophenyl)amine (TAPA) with 1.5 equiv of pyromellitic dianhydride (PMDA)[34]
The advantage of this microwave-assisted reaction is that direct microwave heating is able to reduce chemical reaction times and is known to reduce side reactions, increase yields, and improve reproducibility of synthesis condition[49,50,51]
Summary
A number of technologies for fuel-gas desulfurization (FGD) have been developed using techniques such as lime scrubbing, ammonia scrubbing, and physical absorption via organic solvents, the disadvantages of these processes are prohibitive, including low efficiency and generation of huge amounts of inorganic salts, wastewater, and organic solvents[5,6,7,8]. Ionic liquids (ILs), which are composed of cation/anion combinations, have received much attention from researchers owing to their specific properties, including negligible vapor pressure, high thermal and chemical stability, and high loading capacity[10,11,12,13]. From these properties, the ILs can be functionalized into chemical adsorption processes. The chemical interaction between SO2 and amine groups in the ILs constructs a charge-transfer complex[18, 19], which forms relatively unstable ionic structure that can reduce the energy requirement for SO2 desorption[20]. Bein et al have suggested a new functionalization method by introducing modulator agents into the one-pot synthesis[38]
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