Sulfur
dioxide (SO2) is an acidic and toxic gas and
its emission from utilizing energy from fossil fuels or in industrial
processes harms human health and environment. Therefore, it is of
great interest to find new materials for SO2 sorption to
improve classic flue gas desulfurization. In this work, we present
SO2 sorption studies for the three different metal–organic
frameworks MOF-177, NH2-MIL-125(Ti), and MIL-160. MOF-177
revealed a new record high SO2 uptake (25.7 mmol·g–1 at 293 K and 1 bar). Both NH2-MIL-125(Ti)
and MIL-160 show particular high SO2 uptakes at low pressures
(p < 0.01 bar) and thus are interesting candidates
for the removal of remaining SO2 traces below 500 ppm from
flue gas mixtures. The aluminum furandicarboxylate MOF MIL-160 is
the most promising material, especially under application-orientated
conditions, and features excellent ideal adsorbed solution theory
selectivities (124–128 at 293 K, 1 bar; 79–95 at 353
K, 1 bar) and breakthrough performance with high onset time, combined
with high stability under both humid and dry SO2 exposure.
The outstanding sorption capability of MIL-160 could be explained
by DFT simulation calculations and matching heat of adsorption for
the binding sites Ofuran···SSO2 and OHAl‑chain···OSO2 (both ∼40 kJ·mol–1) and Ofuran/carboxylate···SSO2 (∼55–60 kJ·mol–1).
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.
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