(397g) Dmof-1 As a Representative MOF for SO2 Adsorption in Both Humid and Dry Conditions

Acid gases are pervasive in energy applications ranging from CO₂ capture from flue gas to solid oxide fuel cells powered by syngas. MOFs are potentially useful adsorbents in many of these applications, but the behavior of MOFs in the presence of acid gases is relatively unstudied. DMOF is known for exhibiting partial water stability, and functionalization of its BDC ligand with methyl groups has resulted in increased stability towards water vapor. In addition, it has been shown that varying the metal node of the parent DMOF material results in different mechanisms of structural degradation in the presence of water. The variety of both metal substitution and ligand substitutions available to DMOF provides an interesting set of isostructural materials for assessing acid gas interactions and degradation in MOFs. In this work, DMOF 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 water stability, but also stability towards 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 provided the second most stable material. These results follow the prediction of the Irving-Williams series of metal node / ligand bond strengths.