DMOF-1 as a Representative MOF for SO₂ Adsorption in Both Humid and Dry Conditions

Abstract

The mixed-ligand metal–organic framework (MOF) DMOF-1 has been successfully synthesized via ligand: 2,3,5,6-tetramethylterephthalic acid (TM), 9,10-anthracenedicarboxylic acid (ADC), 1,4-naphthalenedicarboxylic acid (NDC), 2,5-dimethyl terephthalic acid (DM), and metal (Zn, Cu, Ni, Co) substitutions to develop structure–property relationships for adsorption of water and SO2, an acid gas commonly found in flue gas streams at ppm-level concentrations. The substitution of bulky ligands, TM and ADC, resulted in not only improved water stability but also stability toward dry SO2, whereas substitution with NDC and DM did not provide water or SO2 stability. ADC-functionalized Zn–DMOF exhibited the greatest stability under humid SO2 exposure of the ligand-functionalized materials that were tested. Metal substitution of Cu into the DMOF–TM structure resulted in the greatest stability of the M–DMOF–TM samples upon exposure to humid SO2, and Ni–DMOF–TM provided the second most stable material. These results follow the prediction of the Irving–Williams series of metal node/ligand bond strengths.

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

“…[15][16][17][18][19][20][21] Among them, MOFs seem most promising due to their outstanding features including reticular synthesis,t unable structure,a nd high porosity. [22][23][24][25] Up to now,t here is still as mall number of MOFs reported for SO 2 adsorption [26][27][28] when compared to CO 2 and CH 4 sorption. Less effort was even given to targeted trace SO 2 removal, that is,h igh SO 2 uptake at low partial pressure.I ng eneral, the capacity of trace SO 2 removal is quantified by the SO 2 uptake amount at apartial pressure of 0.1 bar or even 0.01 bar.…”

“…At the same time,m ethyl groups increase the hydrophobicity and can shield the reactive metalÀlinker bonds to increase the stability of MOFs towards moisture. [25,36] To the best of our knowledge,there are no reports on the use of methyl groups to increase SO 2 affinity and SO 2 /CO 2 selectivity.H erein, we systematically study the methylfunctionalized BDC linker in pillar-layered [Ni 2 (BDC-X) 2 DABCO] {BDC-X = monomethyl (X = M), 2,5-dimethyl (X = DM), and tetramethyl (X = TM) 1,4-benzenedicarbox-ylate/terephthalate;D ABCO = 1,4-diazabicyclo-[2,2,2]octane} referred to as DMOF-X (Figure 1). [37,38] DMOFs with different metals and linkers,m ixed metals, and mixed linkers,i ncluding BDC-TM and Ni-DMOF-TM, were recently tested for SO 2 sorption with the focus on stability in humid conditions.…”

Capture of toxic gases in MOFs: SO2, H2S, NH3 and NOx

“…26) and Zn-DMOF. 27 These comparative results suggest that in the case of Zn-based materials, the robustness of the SBU plays a secondary role in chemical stability against SO 2 , and the fact that they are constructed from a divalent metal that forms labile bonds, 28 makes them more susceptible to collapse. Although MFM-170 contains the Cu 2+ paddlewheel SBU, a cluster frequently instable under harsh conditions such as corrosive or acidic gases, 29,30 it is stable even aer 50 adsorption-desorption cycles of SO 2 .…”

Kinetic stability of metal–organic frameworks for corrosive and coordinating gas capture

“…Further, many materials are stable to corrosive gases in single component studies, but in the presence of humid air a variety of new challenges arise from potential side reactions that form strong acids. 76 For instance, in combination with water vapor, SO2 forms sulfurous acid (H2SO3), and over time in the presence of oxygen it can form SO3 and sulfuric acid (H2SO4). 77 Consequently, SO2 adsorption in humid air, most relevant for industrial applications, is challenging, and linker protonation resulting in the formation of metal sulfites or sulfates can be extremely destructive.…”

“…180 Increased stability towards dry SO2 in pillared Zn 2+ carboxylate MOFs can be achieved by either increasing the steric bulk on the linker, or by replacing Zn 2+ with the more inert Ni 2+ . 76,181 Pyridinic coordination networks SIFSIX-1-Cu and SIFSIX-2-Cu-i can exhibit high and stable uptakes to dry SO2. Consisting of square grids of Cu 2+ and 4,4'-bipyridine or 4,4'dipyridylacetylene pillared by SiF6 2anions, these frameworks exhibit dry SO2 adsorption capacities of 11.01 and 6.90 mmol g -1 , respectively.…”