Highly Selective and Reversible Sulfur Dioxide Adsorption on a Microporous Metal–Organic Framework via Polar Sites

Abstract

It is very challenging to achieve efficient and deep desulfurization, especially in flue gases with an extremely low SO 2 concentration. Herein, we report a microporous metal−organic framework (ELM-12) with specific polar sites and proper pore size for the highly efficient SO 2 removal from flue gas and other SO 2 -containing gases. A high SO 2 capacity of 61.2 cm 3 •g −1 combined with exceptionally outstanding selectivity of SO 2 /CO 2 (30), SO 2 /CH 4 (871), and SO 2 /N 2 (4064) under ambient conditions (i.e., 10:90 mixture at 298 K and 1 bar) was achieved. Notably, the SO 2 /N 2 selectivity is unprecedented among ever reported values of porous materials. Moreover, the dispersion-corrected density functional theory calculations illustrated the superior SO 2 capture ability and selectivity arise from the high-density SO 2 binding sites of the CF 3 SO 3 − group in the pore cavity (S δ+ •••O δ− interactions) and aromatic linkers in the pore walls (H δ+ •••O δ− interactions). Dynamic breakthrough experiments confirm the regeneration stability and excellent separation performance. Furthermore, ELM-12 is also stable after exposure to SO 2 , water vapor, and organic solvents.

Comparative Evaluation of Different MOF and Non‐MOF Porous Materials for SO2 Adsorption and Separation Showing the Importance of Small Pore Diameters for Low‐Pressure Uptake

“…[ 40 ] Further, the reversibility of the SO 2 adsorption at near room temperatures and energy‐efficient recovery is crucial. [ 41 ] The prospective porous materials for reversible physisorption should be microporous ( d pore < 2 nm), as adsorption should occur at low pressures to secure the removal of the relevant trace amounts of SO 2 from flue gases. [ 41 ]…”

“…[ 41 ] The prospective porous materials for reversible physisorption should be microporous ( d pore < 2 nm), as adsorption should occur at low pressures to secure the removal of the relevant trace amounts of SO 2 from flue gases. [ 41 ]…”

Tailoring the Pore Size and Chemistry of Ionic Ultramicroporous Polymers for Trace Sulfur Dioxide Capture with High Capacity and Selectivity

“…The remarkably superior SO 2 uptake capacity of IUPs than that of the ionic monomers at low partial pressure of SO 2 is attributed to the successful construction of ultramicroporous structure and the abundant high‐density ionic sites (Figure 2 B; Supporting Information, Figure S13 and Table S3). Moreover, at a high pressure of 1.0 bar, IUPs show significantly higher SO 2 capture performance [8.12 mmol g −1 for P(Ph‐4MVIm‐Br)] than the reported adsorbents, including organic polymer P(TMGA‐co‐MBA) (4.06 mmol g −1 ), [14] PI‐COF‐m (6.5 mmol g −1 ), [7] other typical porous materials such as activated carbon (3.3 mmol g −1 ), [6] 13X zeolite (2.7 mmol g −1 at 323 K and 0.4 bar), [5a] ELM‐12 (2.73 mmol g −1 ), [8c] comparable with the benchmarking MOFs such as SIFSIX‐2‐Cu‐i (6.90 mmol g −1 ), [8a] NOTT‐300 (8.1 mmol g −1 at 273 K) [8b] (Supporting Information, Table S3). In this adsorption process, fast adsorption has been realized (Supporting Information, Figure S14).…”

“…6-11.6), , SIFSIX-1-Cu (70.7-54.1), SIFSIX-2-Cu-i (89.4-87.1), and .0) (Figure 2 C). [8] It should be noted that the IAST value is only for qualitative comparison since the uptake capacity of CO 2 is much lower than SO 2 . In addition, both CH 4 and N 2 are blocked by the small pore size of the IUPs (Figure 2 A; Supporting Information, S10) with negligible uptake of 0.07 and 0.02 mmol g À1 , respectively.…”

“…Reversible physisorption using porous adsorbents is an energy-efficient and cost-effective process, which has gained considerable attentions. [4] Porous materials including zeolites, [5] activated carbons, [6] covalent organic frameworks (COFs) [7] and metal-organic frameworks (MOFs) [8] have been widely investigated for replacing traditional alkaline solvents. [2,9] Among these porous materials, MOFs with designability and tuneability can be easily decorated with strong binding sites to increase the uptake capacity of SO 2 at ultra-low pressure (SIFSIX-2-Cu-i: 2.31 mmol g À1 at 0.002 bar) [8a] and high pressure (MFM-170: 17.5 mmol g À1 at 1.0 bar) [8f] at 298 K. For crystalline ultramicroporous materials, by introducing inorganic anion (such as BF 4 À and SiF 6…”