Capture and Separation of SO₂ Traces in Metal–Organic Frameworks via Pre‐Synthetic Pore Environment Tailoring by Methyl Groups

Abstract

Herein, we report ap re-synthetic pore environment design strategy to achieve stable methyl-functionalized metalorganic frameworks (MOFs) for preferential SO 2 binding and thus enhanced low (partial) pressure SO 2 adsorption and SO 2 / CO 2 separation. The enhanced sorption performance is for the first time attributed to an optimal pore sizeb yi ncreasing methyl group densities at the benzenedicarboxylate linker in [Ni 2 (BDC-X) 2 DABCO] (BDC-X = mono-, di-, and tetramethyl-1,4-benzenedicarboxylate/terephthalate;D ABCO = 1,4-diazabicyclo[2,2,2]octane). Monte Carlo simulations and first-principles density functional theory (DFT) calculations demonstrate the key role of methyl groups within the pore surface on the preferential SO 2 affinity over the parent MOF. The SO 2 separation potential by methyl-functionalized MOFs has been validated by gas sorption isotherms,i deal adsorbed solution theory calculations,s imulated and experimental breakthrough curves,and DFT calculations.

Adsorption of Sulfur Dioxide in Cu(II)-Carboxylate Framework Materials: The Role of Ligand Functionalization and Open Metal Sites

“… 19 − 32 MOF-177 exhibits a record high SO 2 uptake of 25.7 mmol g –1 at 298 K and 1 bar, but it shows irreversible structural degradation upon desorption. 22 Considering that over 100,000 MOFs are reported to date, 33 samples that are stable to repeated exposure to SO 2 are still relatively rare, including MFM-300(In) (8.28 mmol g –1 ), 23 MFM-300(Sc) (9.4 mmol g –1 ), 24 DMOF (9.97 mmol g –1 ), 25 NU-1000 (10.9 mmol g –1 ), 26 SIFSIX-1-Cu (11.0 mmol g –1 ), 27 NU-200 (11.7 mmol g –1 ), 28 MFM-601 (12.3 mmol g –1 ), 29 MFM-300(Sc)@EtOH (13.2 mmol g –1 ), 24 MOF-808 (15.3 mmol g –1 ), 30 MFM-170 (17.5 mmol g –1 ), 31 and MIL-101(Cr)-4F(1%) (18.4 mmol g –1 ) 32 (uptake given at 298 K and 1 bar of SO 2 ). Systems incorporating open metal sites that are capable of capturing SO 2 are extremely rare.…”

Sulfur Dioxide Capture in Metal‐Organic Frameworks, Metal‐Organic Cages, and Porous Organic Cages

“…[41] On the same line, framework modification to achieve this optimal pore size has been recently implemented by Janiak et al in the Ni-DMOF series. [42] Here, the inclusion of methyl groups through a pre-synthetic approach led to a 15-fold increment in SO 2 uptake in the low-pressure range for the most methylated DMOF (from 0.25 to 3.79 mmol g À 1 of SO 2 at 0.01 bar and 298 K). In this case, the principal interaction of SO 2 with the pore surface is weak hydrogen bonds (methylene group)CÀ H δ + ••• δÀ O(SO 2 ), followed by (SO 2 )S δ + •••π(benzene from organic ligand) interactions.…”

“…On the same line, framework modification to achieve this optimal pore size has been recently implemented by Janiak et al . in the Ni‐DMOF series [42] . Here, the inclusion of methyl groups through a pre‐synthetic approach led to a 15‐fold increment in SO 2 uptake in the low‐pressure range for the most methylated DMOF (from 0.25 to 3.79 mmol g −1 of SO 2 at 0.01 bar and 298 K).…”

Dense open metal sites in a microporous metal–organic framework for deep desulfurization with record‐high sulfur dioxide storage density

“…Highly efficient and selective removal of sulfur dioxide (SO 2 ) from gas mixtures represents one of the most critical operations in industrial processes, for example, flue-gas desulfurization (FGD) and natural gas purification. [1][2][3] Although the currently implemented limestone scrubbing and wet sulfuric acid processes can remove ~95% of SO 2 contamination, still, the residual SO 2 will deactivate the amine solvent in CO 2 -scrubbing and noble catalyst in catalytic reduction of NO x . 4 Furthermore, the wet FGD technology consumes large amounts of energy and water, as well as generates bulky slurry wastes.…”