Efficient SO2 Capture Research Articles

Porphyrin-based schiff-base and aminal nitrogen-rich porous organic polymers for capture of SO2 and CO2

Due to its serious hazards to human health and the environment, the deep removal of sulfur dioxide (SO2) has been of great significance. Thus, it is critical to develop high efficient SO2 capture and sequestration materials in gas purification process. Herein, we reported two novel prophyrin-based nitrogen-rich porous organic polymers (POPs), PrPOA-BP and PrPSN-BP, constructed through the simple catalyst-free condensation reaction. Owing to the strong affinity to SO2 from the conjugate-electron macrocycles structure of prophyrin and nitrogen-rich porous networks, also the high porous structure, these two POPs demonstrated excellent SO2 capture and separation performance with the adsorption uptakes up to 18.2 mmol g−1 (273 K, 1 bar), 13.3 mmol g−1 (298 K, 1 bar), 1.68 mmol g−1 (298 K, 0.01 bar). This very competitive performance has far exceeded most of the prior reported nanoporous materials. Meanwhile, the IAST selectivities of SO2/CO2 (10/90, v/v) could reach 107.8 and 72.0 at 273 and 298 K, 1 bar. This study represents a new type prophyrin-based POPs materials and confirms the intrinsic potential for high efficiency SO2 capture and sequestration.

Highly Selective SO2 Capture by Triazine-Functionalized Triphenylamine-Based Nanoporous Organic Polymers.

The emissions of sulfur dioxide (SO2) from combustion exhaust gases pose significant risks to public health and the environment due to their harmful effects. Therefore, the development of highly efficient adsorbent polymers capable of capturing SO2 with high capacity and selectivity has emerged as a critical challenge in recent years. However, existing polymers often exhibit poor SO2/CO2 and SO2/N2 selectivity. Herein, we report two triazine-functionalized triphenylamine-based nanoporous organic polymers (ANOP-6 and ANOP-7) that demonstrate both good SO2 uptake and high SO2/CO2 and SO2/N2 selectivity. These polymers were synthesized through cost-effective Friedel-Crafts reactions using cyanuric chloride, 3,6-diphenylaminecarbazole, and 2,2',7,7'-tetrakis(diphenylamino)-9,9'-spirobifluorene. The resultant ANOPs are composed of triazine and triphenylamine units and feature an ultramicroporous structure. Remarkably, ANOPs exhibit impressive adsorption capacities for SO2, with uptakes of approximately 3.31-3.72 mmol·g-1 at 0.1 bar, increasing to 9.52-9.94 mmol·g-1 at 1 bar. The static adsorption isotherms effectively illustrate the ability of ANOPs to separate SO2 from SO2/CO2 and SO2/N2 mixtures. At 298 K and 1 bar, ANOP-6 shows outstanding selectivity toward SO2/CO2 (248) and SO2/N2 (13146), surpassing all previously reported triazine-based nanoporous organic polymers. Additionally, dynamic breakthrough tests demonstrate the superior separation properties of ANOPs for SO2 from an SO2/CO2/N2 mixture. ANOPs exhibit a breakthrough time of 73.1 min·g-1 and a saturated SO2 capacity of 0.53 mmol·g-1. These results highlight the exceptional adsorption properties of ANOPs for SO2, indicating their promising potential for the highly efficient capture of SO2 from flue gas.

Porous Organic Polymers for Efficient and Selective SO2 Capture from CO2-rich Flue Gas.

The quest for effective technologies to reduce SO2 pollution is crucial due to its adverse effects on the environment and human health. Markedly, removing a ppm level of SO2 from CO2-containing waste gas is a persistent challenge, and current technologies suffer from low SO2/CO2 selectivity and energy-intensive regeneration processes. Here using the molecular building blocks approach and theoretical calculation, we constructed two porous organic polymers (POPs) encompassing pocket-like structures with exposed imidazole groups, promoting preferential interactions with SO2 from CO2-containing streams. Markedly, the evaluated POPs offer outstanding SO2/CO2 selectivity, high SO2 capacity, and an easy regeneration process, making it one of the best materials for SO2 capture. To gain better structural insights into the notable SO2 selectivity of the POPs, we used dynamic nuclear polarization NMR spectroscopy (DNP) and molecular modelling to probe the interactions between SO2 and POP adsorbents. The newly developed materials are poised to offer an energy-efficient and environment-friendly SO2 separation process while we are obliged to use fossil fuels for our energy needs.

Tuning the structure of N-methyldiethanolamine-based deep eutectic solvents for efficient and reversible SO2 capture.

Three cheap DESs comprising of N-methyldiethanolamine (MDEA) and imidazole (Im), 1,2,4-triazole, and tetrazole were investigated for capturing SO2 at low concentrations. Surprisingly, with the addition of Im, the SO2 absorption capacity and desorption efficiency were improved. Spectroscopic analysis and quantum chemical calculations confirmed that MDEA-Im effectively and reversibly captured SO2 through the hydrogen bond network and synergistic action between MDEA and Im.

Aminosiloxane having double absorption sites with low viscosity for efficient SO2 capture

The viscosity and absorption capacity are important factors in evaluate the performance of SO2 absorbent, but it is not an easy task to balance the contradiction between them. Herein, we designed and synthesized a novel aminosiloxane (3-diethylaminomethyl-1,1,3,3-tetramethyl-disiloxyalkyl methyl)-diethylamine (DTDA) with double absorption sites. This absorbent has low viscosity before and after absorption, with 3.41 mPa·s and 180.00 mPa·s at 303.15 K, respectively. The absorption capacities of DTDA can reach 3.42 mol/mol (303.15 K, 1.00 atm) and 1.71 mol/mol (303.15 K, 0.02 atm). The desorption of SO2 can be realized at 363.15 K with good cyclic absorption performance. Moreover, with the introduction of dimethyl silicone oil (DSO), a mixed absorption system (DTDA-DSO) with liquid-liquid phase-change behaviors was obtained. The mixed absorption system not only shows better thermal stability but also needs lower thermal desorption energy consumption. The excellent absorption performance of DTDA-DSO system makes them have great potential in the field of SO2 capture and could provide strong support for their industrial application.

High-performance electrospun polystyrene-based nanofiber membrane for efficient SO2 capture

It is essential to design a stable membrane material to solve the pollution produced by SO2 emissions. This study aims to fabricate polystyrene (PS) nanofiber membranes, which are applied for flue gas desulfurization. PS nanofiber membranes are fabricated via electrospinning with porous polypropylene (PP) membrane as the support and high hydrophobic PS as the main membrane material. The modified membranes are characterized by scanning electron microscopy, true color confocal microscopy and other analyticalmethods, and the effects of mixed solvent ratio and polymer concentration on the desulfurization performance and on the stability of PS nanofiber membranes are investigated. The results suggest that an optimum hydrophobicity of PS nanofiber membrane is obtained with a water contact angle of 145°, when the polymer concentration is 5 %. The average pore size of PS nanofiber membrane is 1.56 μm, and the liquid entry pressure of water (LEPw) is 0.26 bar and the roughness of membrane is 5.674 μm. The desulfurization performance of the PS nanofiber membrane is better than that of the PP membrane. The SO2 absorption flux of the modified membranes keeps at 7.2 × 10−4 to 7.6 × 10−4 mol·m−2·s−1 during 5 h operating, and SO2 removal efficiency is up to 50 %, which potentially makes contributions to air pollution reduction.

A novel robust phosphate-functionalized metal–organic framework for deep desulfurization at wide temperature

The need to decrease environmental pollution, reduce energy consumption and produce high-purity chemicals has become an increasingly important driving force for sulfur dioxide (SO2) capture. The efficient capture of low concentrations of SO2, a highly corrosive acid gas that is not typically present in high concentrations in industrial settings, is a major challenge. Herein, a novel phosphate-functionalized metal–organic framework, ZU-801, is designed with precisely controlled pore sizes and chemical environment to achieve excellent adsorption capacity for SO2 (1.44 mmol g−1 at 0.002 bar, 2.00 mmol g−1 at 0.01 bar) and high IAST selectivities for SO2/CO2 (145), which provides great potential for selective capture of SO2. ZU-801 shows excellent stability to air, water, SO2, strong acid and strong base solutions, and it is thermally stable up to 733 K. Additionally, ZU-801 exhibits outstanding separation ability in removing SO2 from SO2/CO2 mixtures at temperature as high as 383 K or in humid environments. This work demonstrates the potential of designing ion-functionalized ultramicroporous materials with tailored pore sizes and porous chemical environments for efficient capture and separation of SO2 and sheds light on designing stable high-performance materials that operate at high temperatures.

Red mud with enhanced dealkalization performance by supercritical water technology for efficient SO2 capture

The total de-alkalization treatment of industrial solid waste red mud (RM) has been a worldwide challenge. Removing the insoluble structural alkali fraction from RM is the key to enhancing the sustainable utilization of RM resources. In this paper, supercritical water (SCW) and leaching agents were used for the first time to de-alkalize the Bayer RM and to remove sulfur dioxide (SO2) from flue gas with the de-alkalized RM slurry. The results showed that the optimum alkali removal and Fe leaching rates of RM-CaO-SW slurry were 97.90 ± 0.88% and 82.70 ± 0.95%, respectively. Results confirmed that the SCW technique accelerated the disruption of (Al–O) and (Si–O) bonds and the structural disintegration of aluminosilicate minerals, facilitating the conversion of insoluble structural alkalis to soluble chemical alkalis. The exchangeable Ca2+ displaced Na+ in the remaining insoluble base, producing soluble sodium salts or alkalis. CaO consumed SiO2, which was tightly bound to Fe2O3 in RM, and released Fe2O3, which promoted Fe leaching. RM-SCW showed the best desulfurization performance, which maintained 88.99 ± 0.0020% at 450 min, followed by RM-CaO-SW (450 min, 60.75 ± 6.00%) and RM (180 min, 88.52% ± 0.00068). The neutralization of alkaline components, the redox of metal oxides, and the liquid-phase catalytic oxidation of Fe contributed to the excellent desulfurization performance of the RM-SCW slurry. A promising approach shown in this study is beneficial to RM waste use, SO2 pollution control, and sustainable growth of the aluminum industry.

Efficient SO2 capture and conversion to cyclic sulfites by protic ionic liquid-based deep eutectic solvents under mild conditions

SO2 capture has been a research hotspot targeting mitigation of SO2 emission, and the subsequent conversion of SO2 is an ingenious protocol, which can avoid regeneration of absorbents and realize utilization of SO2 simultaneously. To this end, a series of protic ionic liquids (PILs)-based deep eutectic solvents (DESs) composed of N-alkylimidazole hydrochloride-based PILs and azoles were designed for the capture and conversion of sulfur dioxide. Among them, [MImH]Cl/2-MIm (1:1) exhibited SO2 loading capacity as high as 1.45 g/g at 1.0 bar and 20 °C, and remarkable SO2 solubility up to 0.56 g/g were achieved at low concentrations (0.6 vol%, 20 °C). In particular, the absorbed SO2 can be directly converted to cyclic sulfites through cycloaddition reaction catalyzed by these DESs under very mild condition (30 °C and 1.0 bar of SO2) without any solvent of additive. By using gas chromatograph-mass spectrometer (GC-MS), yields of cyclic sulfites were determined to be excellent for styrene oxide (98 %) and 1,2-epoxybutane (97 %), and moderate for the sterically hindered epoxides (56 %–76 %). Recycling experiments proved that these DESs maintained good absorption and catalytic performance after five cycles. Furthermore, the absorption and catalytic mechanism were studied by Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR) spectroscopies, and theoretical calculations, revealing the multi-site absorption mechanism and synergic catalysis in PIL-based DES.

Efficient SO2 capture at ultra-low concentration using a hybrid absorbent of deep eutectic solvent and ethylene glycol

Deep eutectic solvents (DESs) are considered as the highly effective absorbents for sulfur dioxide (SO2) capture. However, the high viscosity of DESs and the resulting slow absorption rate as well as low absorption capacity at low SO2 concentration seriously hinder their industrial application. In this study, DES of N-methyldiethanolamine (MDEA) and imidazole (Im) is simply blended with ethylene glycol (EG) forming a hybrid absorbent, namely MDEA/Im-EG, which exhibits extremely high SO2 capture capacity at low concentration. In particular, SO2 capture capacity in MDEA/Im-EG (molar ratio = 1:1) reaches 0.446 g SO2/g absorbent at 293.2 K with SO2 concentration of 2000 ppm. Moreover, the corresponding desorption enthalpy is only −40.67 kJ/mol. To well understand the results, thermodynamic analysis of SO2 capture is performed and the SO2 capture mechanism is speculated by nuclear magnetic resonance and Fourier transform infrared spectroscopy.

Process compatible desulfurization of NSP cement production: A novel strategy for efficient capture of trace SO2 and the industrial trial

Cement industry contributes to more and more SO2 emission due to utilization of alternative raw materials and fuels, whereas the available calcium-based dry flue gas desulfurization (FGD) technologies present low efficiency due to slow reversible de-SO2 reactions and short gas-solid contact time in the preheater. In the present study, the SO2 capture potentials of CaCO3, CaO, and Ca(OH)2 in the preheater environment were maximized by introducing V2O5-based catalyst and selecting optimal reaction temperature, and the de-SO2 mechanism was extensively discussed. The results showed that the de-SO2 efficiency of calcium-based adsorbents increased by 10–57 times as SO2 was effectively oxidized to SO3 in the presence of V2O5-based catalyst, then maximum de-SO2 efficiency of 75.5% was achieved using Ca(OH)2 and V2O5-CeO2 at 600 °C. Furthermore, CaCO3 assisted by V2O5-CeO2 also had a de-SO2 efficiency of 65.6%. Subsequently, a novel process compatible FGD technology was designed to maximize the de-SO2 ability of raw meal in the preheater by adding V2O5-based catalyst and humidification, the SO2 concentration of flue gas reduced from 1000 mg/Nm3 to less than 100 mg/Nm3 in the industrial-scale trial, as more sulfur was solidified into clinker in the form of alkali sulfate without reducing its properties. This novel process compatible de-SO2 strategy is of real significance for reducing SO2 emission of cement industry at low economic cost.

Efficient SO2 capture using an amine-functionalized, nanocrystalline cellulose-based adsorbent

Adsorbents made from cellulose derivatives have been widely studied for removal of contaminants such as toxic gases, pharmaceutical ingredients, dyes, and metals due to the availability, cost-effectiveness, and non-contaminating nature of these adsorbents. In this study, amine-functionalized cellulose is proposed as a green adsorbent for SO2 capture. Cellulose nanocrystals were chemically modified with ethylenediamine (EDA) using a solvent-free method. The surface modification was confirmed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), solid-state carbon nuclear magnetic resonance (13C NMR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and elemental analysis. The effects of functionalization time, temperature, and amount of EDA on the SO2 capture capacity were assessed. During these investigations, the highest adsorption capacity obtained was 2.07 mg-SO2/gsorbent, which is six times higher than for pristine nanocrystalline cellulose (NCC) used under the same conditions. Furthermore, the effect of various operating adsorption temperatures and flow rates was investigated. When the temperature was reduced, there was a significant increase in capture capacity and breakthrough time, confirming an adsorption mechanism for SO2 capture. It was also confirmed that as the flow rate of the feed gas increases, the breakthrough time decreases, as expected, with a steeper breakthrough curve, because of the faster transport of the adsorbate molecules.

Mn-CUK-1: A Flexible MOF for SO2, H2O, and H2S Capture.

The environmentally benign metal-organic framework (MOF) CUK-1 based on 2,4-pyridine dicarboxylate has been prepared for the first time using Mn(II) as the inorganic node and water as the only solvent. Mn-CUK-1 shows reversible and efficient capture of H2O, SO2, and H2S. Compared to previously studied Co(II) and Mg(II) versions of the same MOF, Mn-CUK-1 also exhibited unique temperature-induced structural flexibility due to organic linker torsion, as detailed by variable-temperature single-crystal X-ray diffraction studies. Owing to this inherent solid-state flexibility, Mn-CUK-1 showed stepwise adsorption for polar gases, which induce structural deformations upon adsorption, while the nonpolar guest adsorbates were reversibly sorbed in a more classical manner. Notably, Mn-CUK-1 demonstrates the highest reported H2S capacity-to-surface area ratio among MOFs that are chemically stable toward this reactive acidic molecule. Moreover, Mn-CUK-1 displays exceptional structural stability in the presence of high relative humidity and corrosive gases and shows soft crystalline behavior triggered by changes in both the adsorption temperature and guest molecule identity.

Responsive Porous Material for Discrimination and Selective Capture of Low-Concentration SO2

The efficient removal of low-concentration SO2 is of great significance but challenging due to the competitive adsorption of CO2. Herein, we report the efficient capture of low-concentration SO2 with high selectivity over CO2 by Mn(INA)2 (INA = isonicotinate) with a designed pore structure. Notably, the channels of Mn(INA)2 exhibit large cavities and narrow bottlenecks, leading to the exclusion of the larger molecules of N2 and CH4. An interesting phenomenon was observed through single-crystal X-ray diffraction experiments where SO2 “opened” the bottlenecks and entered the cavities via the rotation of the pyridine ring (12.2°) to enlarge the cavities to accommodate SO2 molecules. These responsive properties of Mn(INA)2 to SO2 molecules afford high SO2/CO2 separation selectivity. In addition, first-principles dispersion-corrected density functional theory (DFT-D) calculations elucidate that the high-density host–guest interactions including duple Sδ+···Oδ− electrostatic interactions, multiple Hδ+···Oδ− dipole–dipole interactions, and guest–guest interactions between SO2 molecules are responsible for the sensitive response of the material toward low-concentration SO2 (2000 ppm). The efficient SO2 capture properties of Mn(INA)2 are further demonstrated by the breakthrough experiments. Moreover, the material is stable and easy to scale up, which makes it promising for low-concentration SO2 removal.

An ultra-stable Zr(IV)-MOF for highly efficient capture of SO2 from SO2/CO2 and SO2/CH4 mixtures

• A novel ultra-stable Zr(IV)-MOF (HBU-20) was synthesized by solvothermal method. • HBU-20 shows highly efficient capture of SO 2 over CO 2 and CH 4 . • Theoretical simulations exhibit the importance of host–guest weak interactions. • Gas breakthrough experiments prove its’ application in deep desulfurization. Flue gas and natural gas deep desulfurization is still very challenging, so new absorbent is highly desired. In this work, a novel stable porous Zr(IV)-MOF (HBU-20) has been designed and synthesized. HBU-20 possesses a high BET surface area of 1551.1 m 2 /g and the pore volume achieves 0.896 cm 3 /g. More importantly, the compound shows a high SO 2 adsorption capacity of 6.69 mmol/g at 298 K and 100 kPa, and the higher IAST selectivitives of SO 2 /CO 2 (v/v, 1:99, 56.7) and SO 2 /CH 4 (v/v 1:99, 246) have been accordingly obtained. Theoretical simulations proved host–guest interactions should be responsible for efficient SO 2 capture. Furthermore, the excellent separation performance of HBU-20 had also been evaluated by dynamic breakthrough experiments under ambient condition. The experimental selectivities of SO 2 /CO 2 and SO 2 /CH 4 (v/v 1:99) achieve 81.1 and 117.6, respectively. The research indicates HBU-20 is a promising absorbent for deep desulfurization of flue gas and natural gas.

Solidothermal synthesis of nitrogen-decorated, ordered mesoporous carbons with large surface areas for efficient selective capture and separation of SO2

As a typical corrosive and toxic exhaust gas, the effective elimination of sulfur dioxide is of great importance for flue gas desulfurization. Yet the facile synthesis of adsorbents with high capture capacity (especially at low partial pressures) as well as excellent stability remains a challenge. Herein, we reported the preparation of N-functionalized ordered mesoporous carbons through a solvent-free self-assembly strategy for selective capture and separation of SO2 via enhanced base-acid host–guest interaction. The N-doped ordered mesoporous carbons were synthesized using Pluronic F127, terephthalaldehyde, and m-aminophenol as raw materials, then followed by activation with KOH. The synthesized N-OMC-T samples are found to exhibit large specific surface areas (∼1191 m2/g) and multifunctional nitrogen base sites. The synthesized K-N-OMC-T samples show excellent SO2 capacity with 13.15 mmol/g at 1.0 bar and 25 °C, and the corresponding IAST selectivities for SO2/N2 and SO2/CO2 reach up to 195.8 and 16.4 (25 °C), respectively. The breakthrough tests further demonstrate the impressive elimination of SO2 from SO2/CO2/N2 gas mixture by K-N-OMC-T samples. Thus, it is believed that the possibility for selective SO2 capture from flue gas is for K-N-OMC-T samples.

CTAB-controlled synthesis of phenolic resin-based nanofiber aerogels for highly efficient and reversible SO2 capture

• The structure and SO 2 capture performance of aerogels are tunable by CTAB. • High SO 2 capacity and excellent SO 2 /N 2 and SO 2 /CO 2 electivity were achieved. • A fast SO 2 adsorption rate was achieved with less than 5 min. • AG-0.15 aerogels showed good reversibility in adsorption–desorption cycles. Currently available aerogels as effective adsorption materials for capture of trace sulfur dioxide (SO 2 ) are unfavorable from the perspective of deep desulfurization technologies. Herein, four phenolic resin-based aerogels with controlled structures varying from spherical (∼1 μm) to nanofiber (∼20 nm) were prepared and characterized using hexadecyl trimethyl ammonium bromide (CATB) as a soft template. It is demonstrated that adjusting the usage amount of CTAB from 0.00 to 0.15 g could effectively regulate SO 2 adsorption capacities of phenolic resin-based aerogels. AG-0.15 nanofiber aerogel exhibited an outstanding SO 2 uptake through a swelling mechanism (10.58 mmol g −1 at 298.2 K, 1.0 bar), and displayed a very high SO 2 /N 2 selectivity (7271 at 298.2 K). Moreover, AG-0.15 nanofiber aerogel also had excellent performance for selective capture of 2000 ppm SO 2 in the mixed SO 2 /N 2 /CO 2 gases through dynamic column breakthrough experiments. Overall, phenolic resin-based nanofiber aerogels are perceived as a promising adsorbent for effective removal of trace SO 2 from flue gas.

Effective absorption of SO2 by imidazole‐based protic ionic liquids with multiple active sites: Thermodynamic and mechanical studies

AbstractIn view of the environmental hazards caused by SO2, the development of efficient SO2 capture technology has important practical significance. In this work, a low‐viscosity protic ionic liquids containing imidazole (Im), ether linkage, and tertiary amine structure was synthesized by acid–base neutralization of tris(3,6‐dioxaheptyl)amine (TMEA) and Im for SO2 absorption. The results showed that the solubility of SO2 in [TMEA][Im] reached 12.754 mol kg−1 at 298.2 K and 1 bar and the ideal selectivity of SO2/CO2 (1/1) is 141.7 at 1 bar. Furthermore, [TMEA][Im] can be reused and the SO2 absorption performance was not significantly reduced after five cycles. In addition, the absorption of low‐concentration SO2 (2000 ppm) in [TMEA][Im] was also tested. Further spectroscopic research and thermodynamic analysis suggested that the high SO2 uptake by [TMEA][Im] was caused by the synergistic effect of physical and chemical absorption.

NH2-MIL-125 filled mixed matrix membrane contactor with SO2 enrichment for flue gas desulphurization

Membrane absorption is a convenient and efficient flue SO2 capture technology. In this study, NH2-MIL-125 filled mixed matrix membrane contactor (MMMC) is constructed by Non-solvent Induced Phase Separation (NIPS) method. The functional groups and metal active sites on the surface of NH2-MIL-125(Ti) exhibit high affinity for SO2. The microporous structure of NH2-MIL-125(Ti) provides storage for adsorbed SO2, which is conducive to the formation of SO2 enrichment zone in the membrane. The membrane morphology, wetting resistance, and light responsiveness et al of MMMC have been tested. The combination of NH2-MIL-125(Ti) adsorption and membrane absorption process effectively promotes the transfer of gas molecules in the membrane pores. The SO2 absorption flux of MMMC filled by NH2-MIL-125(Ti) has a significant increment, reaching 8.81 × 10−4 mol·m−2·s−1 and 9.77 × 10−4 mol·m−2·s−1 under non-light and visible light conditions respectively, which is comparability with results in literature. The membrane phase mass transfer coefficient calculated by Wilson model is 149.6 s·m−1, which shows the low resistance in membrane. The SO2 absorption flux keep stable after 4 cycles of tests. The membrane contactor coupled with function fillers enhances the SO2 capture ability and further promotes the enrichment of SO2, which has favorable development foreground.

Post modification of Oxo-clusters in robust Zirconium-Based metal organic framework for durable SO2 capture from flue gas

The efficient capture of SO2 after the combustion of fossil fuels is of great challenge as the low SO2 concentration (<500 ppm) and coexisting with CO2, water, O2 in flue gas. Robust zirconium-based MOFs possessing accessible polar sites usually have high SO2 adsorption capacity but poor durably in adsorption desulfurization due to the acidic sulfate deposition on the Zr-O cluster. Herein, a Zr-O cluster post-modification method was introduced in a Zr-MOF (MOF-808) to form EDTA-MOF-808 (EDTA, ethylene diaminetetraacetic acid) for selective and durable removal of SO2. The introduction of EDTA not only improve their SO2 adsorption capacity, but also sharply increase their SO2/CO2 selectivity (57.2 vs 8.9) and SO2/N2 selectivity (1915.8 vs 292.7) at low SO2 partial pressure. Moreover, the synergistic effects of dipole and hydrogen bonding interaction between SO2 and EDTA in EDTA-MOF-808 make the capture of SO2 in a reversible manner, which can prevent the formation of S(VI) species in Zr-MOF. DFT calculation confirmed that SO2 was interacted with EDTA through moderate dipole–dipole interaction (S(SO2) with N(EDTA)) and hydrogen bonds (H(–COOH) with O(SO2)). Systematic investigations including thermodynamic SO2 adsorption, dynamic breakthrough experiments, stability tests and DFT-calculations in both MOF-808 and EDTA-MOF-808 confirmed the efficient performance of post modification of Zr-O clusters with EDTA in Zr-MOFs for durable SO2 capture.