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

Herein, we report a pre-synthetic pore environment design strategy to achieve stable methyl-functionalized metal-organic frameworks (MOFs) for preferential SO2 binding and thus enhanced low (partial) pressure SO2 adsorption and SO2/CO2 separation. The enhanced sorption performance is for the first time attributed to an optimal pore size by increasing methyl group densities at the benzenedicarboxylate linker in [Ni-2(BDC-X)(2)DABCO] (BDC-X=mono-, di-, and tetramethyl-1,4-benzenedicarboxylate/terephthalate; DABCO=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 SO2 affinity over the parent MOF. The SO2 separation potential by methyl-functionalized MOFs has been validated by gas sorption isotherms, ideal adsorbed solution theory calculations, simulated and experimental breakthrough curves, and DFT calculations.

Automated summary

In this study, a pre-synthetic pore environment design strategy was utilized to create stable methyl-functionalized metal-organic frameworks (MOFs) for enhanced low pressure SO2 adsorption and separation from CO2. The key role of increasing methyl group densities at the benzenedicarboxylate linker in optimizing pore size was demonstrated for the first time. Various methods, including gas sorption isotherms, theoretical calculations, simulations, and DFT calculations, were used to validate the SO2 separation potential of methyl-functionalized MOFs.