Effect of Ionic Liquid Impregnation in Highly Water-Stable Metal–Organic Frameworks, Covalent Organic Frameworks, and Carbon-Based Adsorbents for Post-combustion Flue Gas Treatment

Abstract

In this work, a comparative study on water-stable microporous adsorbents is conducted computationally in the quest of a suitable adsorbent for post-combustion CO2 capture. In this regard, three metal–organic frameworks (MOFs), two covalent organic frameworks (COFs), and a single-wall carbon nanotube (SWCNT) are investigated under the same flue gas conditions. The simulation results show that the pure component adsorption capacity for CO2 follows the order SWCNT > InOF-1 > COF-300 > UiO-66 > COF-108 > ZIF-8 at post-combustion conditions. Further, these materials are impregnated with ionic liquids to examine the effect on the CO2 separation ability of these materials. The adsorption capacity enhances by incorporating ionic liquids, especially [EMIM]­[SCN] compared to [EMIM]­[BF4] as a result of a stronger interaction and being less bulky in nature. We further tested the effect of the presence of other components of flue gas on the selectivity of CO2 over N2, and we found that the presence of SO2 and water vapor reduces the CO2 selectivity in all of the materials considered in this work. Performance in terms of CO2 selectivity of these materials is tested in the presence of all major components of flue gas, and we found that, under the same thermodynamic conditions, it follows the order InOF-1 > COF-300 > UiO-66 > SWCNT > COF-108 ≈ ZIF-8. The CO2/N2 selectivity increases significantly after impregnating materials with ionic liquids. In the presence of water, InOF-1 completely discard N2, showing infinitely large selectivity for CO2/N2. In humid conditions, the difference in selectivity between pristine and composite materials decreases significantly.

State of the art of ionic liquid‐modified adsorbents forCO2capture and separation

“…N 2 ,61 or both[66][67][68] was also achieved in other studies. The schematic of one of these adsorbents namely [C 2 mim][SCN]@Cu-BTC was shown in Figure3and ILs were present in both pores and surface of supports.…”

“…53 There is no doubt that both ILs and supports play an important role in CO 2 separation for supported IL adsorbent. 61 [Tf 2 N]@ZIF-8 showed stronger interaction with CO 2 , resulting in better CO 2 separation performance than other IL@ZIF-8 with the same anion.…”

“…Similarly, Zhu et al70 drew the same conclusion.For supported conventional IL adsorbents, the cation and anion play the equal important roles in CO 2 capture. Maurya et al61 studied the CO 2 separation performance of IL-modified adsorbents including two conventional ILs and six supports by the simulation method. It was found that [C 2 mim][SCN]@single-wall carbon nanotube (SWCNT) shows the highest CO 2 adsorption capacity of 3.50 mmolCO 2 /g-adsorbent under 30 C and 0.05 MPa.…”

Recent progress in the development of ionic liquid‐based mixed matrix membrane for CO 2 separation: A review

“…Previous work showed that these ILs are capable of separating CO 2 from other gases such as CH 4 and N 2 131 . Therefore, RTILs have been thoroughly investigated in the application of natural gas purification 132,133 and flue gas treatment 134‐136 …”

Multi-Level Computational Screening of in Silico Designed MOFs for Efficient SO2 Capture

“…Zhang et al 20 computationally studied SO 2 capture from SO 2 /CO 2 and SO 2 /N 2 mixtures using porous aromatic frameworks (PAFs) where it has been concluded that the incorporation of the functional groups (−CH 3 , −CN, −COOH, −COOCH 3 , −OH, −OCH 3 , −NH 2 , and −NO 2 ) into PAF-1 boosts the SO 2 selective behavior of the materials especially below 10 bar. Maurya and Singh 34 simulated the SO 2 adsorption in several adsorbents (COF-108, COF-300, single-walled carbon nanotube (SWCNT), InOF-1, UiO-66, and ZIF-8) around ambient conditions where the SO 2 uptakes of UiO-66 and ZIF-8 (∼5 mol/kg) are found to be several folds lower than that of SWCNT (∼23 mol/kg). Li et al 9 performed grand canonical Monte Carlo (GCMC) simulations to investigate the SO 2 capture from SO 2 /CO 2 and SO 2 /N 2 mixtures using UiO-66 and its functionalized variants where it has been concluded that UiO-66-(COOH) 2 and UiO-66-COOH exhibit two of the highest adsorption selectivities at low pressures (SO 2 /CO 2 and SO 2 /N 2 selectivity higher than ∼40 and 3000, respectively).…”