Competitive adsorption of methyl bromide and water on metal

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Competitive adsorption of methyl bromide and water on metal catecholates: Insights from density functional theory Nathaniel Scott Bobbitt, and Randall Q. Snurr Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.8b04377 • Publication Date (Web): 30 Nov 2018 Downloaded from http://pubs.acs.org on December 4, 2018

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Industrial & Engineering Chemistry Research

Competitive adsorption of methyl bromide and water on metal catecholates: Insights from density functional theory N. Scott Bobbitt and Randall Q. Snurr∗ Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208 E-mail: [email protected] Abstract Density functional theory was used to study the interaction of methyl bromide (MeBr) and water with a large number metal catecholates. Differences in the binding mechanism of MeBr and water result in differences in the adsorption selectivity of the alkaline earth, early, and late transition metals. The binding of water is primarily driven by electrostatic attraction between the water oxygen atom and the metal, which means the alkaline earth and early transition metals heavily favor water over MeBr. For the more electronegative late transition metals, MeBr donates a significant amount of electron density to the metal, which dominates over the electrostatic binding effect. These metals favor MeBr over water, based on single molecule adsorption calculations. However, calculations of simultaneous adsorption of water and MeBr indicate that MeBr adsorption on late transition metals such as Pt and Au is detrimentally affected by the presence of water, while MeBr adsorption on Ca is more resistant to the presence of humidity. Therefore, despite lower single-component selectivity for MeBr, Ca and other alkaline earth metals might offer advantages for MeBr adsorption applications in humid

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Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

environments. Also, in the case of four metals (Sc, Y, Hf, and Ta), MeBr is predicted to dissociate and bind separately to the metal as a Br atom and a methyl group, resulting in a very favorable binding energy (>275 kJ/mol).

Introduction Bromomethane, or methyl bromide (MeBr), is a toxic gas that is a severe irritant to the skin, eyes, and respiratory system. It has been widely used as a pesticide and fumigant, but it is currently being phased out due to concerns about ozone depletion. Despite substantial reductions in recent years, MeBr is still used as an agricultural pesticide in several countries that receive exemptions to use the controlled chemical. In 2014, almost 400 metric tons of MeBr was used under critical use exemptions as an agricultural pesticide in the USA, Canada, and Australia. 1 MeBr is also still used for quarantine and preshipment treatments for international shipments. The permissible exposure limit for MeBr is 20 ppm. 2 Due to the toxicity of MeBr, workers involved in its production or application need respiratory protection. Aside from its health hazards and deleterious effects on the ozone layer, MeBr has been identified as a poison for proton exchange membrane fuel cells. 3–5 Trace amounts of MeBr occur in the atmosphere due to production from natural sources, such as oceanic vegetation 6,7 and terrestrial woodlands. 8 Since MeBr is present in the atmosphere, this could potentially impair the performance of automotive fuel cells, which rely on air as an oxidant. 9 MeBr can be adsorbed onto activated carbon, 10,11 and this strategy is commonly used to recapture MeBr from fumigation chambers. 12 Typically, the MeBr is subsequently destroyed in an aqueous thiosulfate solution 12–14 or via hydrolysis. 10,15 However, the amount of MeBr adsorbed on activated carbon compared to the vapor phase concentration is fairly low, and MeBr uptake is significantly reduced by the presence of humidity. 11,16,17 In general, selective adsorption of target gases in the presence of humidity is a challenging problem. Significant research has been devoted to finding effective sorbents for ammonia, 18–22 CO2 , 23–26 methyl 2


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iodide, 27 and other chemicals 28–30 in the presence of water. Some researchers have tried to improve the adsorption capacity of activated carbon for other gases (notably ammonia) by adding metal sites to the carbon. However, it is difficult to precisely control the metal addition due to the amorphous structure of activated carbon. 31–33 These disadvantages of activated carbon represent an opportunity to develop new sorbents with greater affinity for MeBr and better selectivity for MeBr in the presence of humidity. Metal-organic frameworks (MOFs) are crystalline materials made from metal nodes connected by organic linkers. Since they can be made from thousands of combinations of nodes and linkers in different topologies, MOFs are a very diverse class of materials. Some MOFs are highly porous and have high surface areas that make them well-suited to gas storage and separation, 34 as well as the capture of toxic gases. 35 MOFs are also crystalline, unlike activated carbon, and their regular crystal structure makes it easier to control post-synthetic metallation. 33,36,37 Metal catecholates are an interesting functional group for the enhancement of selective adsorption in porous materials. The geometry of the catecholate leaves the metal site open and easily accessible by the adsorbate. Also, they can be incorporated into MOFs and porous organic polymers and can be made from a variety of metals. 38–41 The ionic character, electron affinity, and orbital occupancy of the metal atom in a catecholate greatly influence the binding strength and selectivity for adsorbing the target molecule. 20,22,42–45 To our knowledge, there is no systematic study of MeBr binding on a wide range of metals currently in the literature. In this work, we have used density functional theory (DFT) to calculate the interaction strength of MeBr with metal catecholates containing metals from the alkaline earth and transition metals. We also compare the binding energy of MeBr on each metal with the binding energy of a water molecule, and we examine simultaneous competitive binding of MeBr and water for a few selected metals. This broad screening allows us to discern trends in the binding behavior of MeBr across the periodic table and identify metals that should

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be the most effective candidates for capturing MeBr in a humid environment.

Computational Methods We modeled the interactions between the metal catecholates, MeBr, and water using DFT and the Gaussian 09 code. 46 The LANL2DZ basis set with effective core potential (ECP) was used for metal atoms, and the 6-311+G(d,p) basis set was used for all non-metal atoms. The exchange-correlation was treated with the M06 functional with 27% Hartree-Fock exchange. 47 In order to determine if this level of theory gives reasonable results for our system, we computed the binding energy for five metals (Mg, Mn, Pt, Zn, and Cd) using several different DFT functionals and basis sets. The results are shown in Figures S1 and S2. We find that the level of theory previously described generally agrees with the other functionals and basis sets. We do note that MeBr binding energies using the M06 DFT functional (paired with the 6-311+G(d,p) basis set and the LANL2DZ ECP) are consistently lower (stronger) compared to B3LYP (paired with the same basis set and ECP) by an average of 16 kJ/mol, and are lower than PBE for Mg, Mn, Zn, and Cd (but not Pt) by an average of 16 kJ/mol. Stoneburner et al. previously reported that M06 gives accurate results for other gases, including water, binding to metal catecholates. 43 We tested several basis sets using the M06 functional (Figure S2). We find that all four basis sets are in close agreement for the binding energy of MeBr on Mg, Mn, and Pt. There is more quantitative disagreement between the four basis sets for Zn and Cd, which both have full 3d shells. Notably, the SDD basis set gives stronger binding energies for Zn and Cd than the other basis sets. However, the qualitative ranking of binding strength among the metals does not change, with Cd having the weakest binding in all cases. The metal catecholates were formed by removing the two protons from the -OH groups in a catechol molecule and adding a divalent metal cation, which is bound to both oxygen atoms. In this work, we use a benzene ring as a proxy for an aromatic MOF linker. In

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previous work we tested different aromatic fragments, including benzene, naphthalene, and imidazole, and found that this did not significantly affect the binding energy or geometry. 48 We found the most favorable adsorbate position by testing at least five different initial configurations for the adsorbate and performing geometry optimizations in Gaussian 09. For systems that involved both MeBr and water molecules, we used more starting geometries to ensure that we found the most favorable position. The binding energies reported here are enthalpies and were calculated as the difference between the energy of the bound adsorbatecatecholate system and the energy of the isolated catecholate and adsorbate molecules at infinite separation. The binding energies were corrected for the basis-set superposition error using the counterpoise method. 49 Orbital analysis and partial charges were computed using the NBO 6.0 software package. 50 Each catecholate was optimized at all possible spins, and the spin state with the lowest energy was used for the binding energy calculations. Most of the catecholates were treated in the high spin state, except for Zr, Hf, Nb, Ta, Re, and Os, which were treated in lower spin configurations for the binding interactions (See Table S1).

Results and Discussion Single Molecule Adsorption We first consider adsorption of a single MeBr molecule onto the metal catecholates under dry conditions. The binding energy of MeBr with each metal catecholate is presented in Figure 1a. The binding energies range from -39 kJ/mol (Cd) to -158 kJ/mol (Ir), and the Row 6 metals W, Re, Os, Ir, and Pt as well as Be, Mg, and Mn have interaction strengths greater than 100 kJ/mol. Binding energies in this range are consistent with chemisorption between the MeBr and the metal atom. Some interesting periodic trends in the binding energy strength emerge in Figure 1a. The binding energy for Be is fairly strong, and the binding energy gets weaker moving down the alkaline earth metals from Be to Sr. The 5



binding strengths for Zn and Cd, which have filled 3d shells, are notably weak compared to other late transition metals. These trends are similar to those we predicted for ammonia, phosphine, and arsine on metal catecholates. 42 Similar to our previous results for ammonia, we find that the alkaline earth metals (Be, Mg, Ca) bind MeBr fairly strongly via Coulomb attraction. The early transition metals exhibit weak binding, and the highly electronegative Row 6, late transition metals (Os, Ir, Pt) bind MeBr the strongest due to accepting more electron density from the adsorbate. Since most practical applications of MeBr capture will likely occur in the presence of humidity, it is important to compare the behavior of MeBr with water. Figure 1b shows the difference in the binding energy of a single water molecule on the metal catecholate and the binding energy of MeBr. A positive difference (blue) indicates that the metal is more selective for water than MeBr, while a negative value (yellow or red) indicates the metal is more selective for MeBr. Clearly the metals on the left side of the periodic table significantly favor water, and this selectivity shifts to be more favorable for MeBr for metals farther to the right and down in the periodic table. Ir, Pt, and Au show the highest selectivity for MeBr over water, and while Be and Mg have a strong affinity for MeBr, they also show poor selectivity. We can understand the selectivity of metals for either water or MeBr by considering the different binding mechanisms of these molecules. The alkaline earth metals and early transition metals have low electronegativity; therefore, the two oxygen atoms connecting the metal to the aromatic ring withdraw a significant amount of electron density, leaving the metal highly charged. For example, in the isolated catecholate, Mg has a partial charge of 1.66 e and Ca has a charge of 1.64 e, while the later transition metals like Pt and Ag have lower charges (0.60 e and 0.70 e, respectively). For a full list of partial charges on the metal atoms see Table S2. Water binding to the metal is primarily driven by Coulomb attraction between the nega-

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(a)

(b)

Figure 1: (a) Binding energies (kJ/mol) of MeBr with various metal catecholates. (b) Difference in binding energy of MeBr and the binding energy of a water molecule. Negative values (red) indicate a stronger binding energy for MeBr, and positive values (blue) indicate a stronger binding energy for water. tively charged oxygen atom of water and the positively charged metal. Therefore, the metals on the left side of the periodic table—those with low electronegativities and large positive

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charges—favor binding of water over the less polar MeBr. However, MeBr binding to the metal involves a combination of electrostatic attraction and sharing of electrons between the Br and the metal, forming a partial bond. As seen in Figure 2, the Coulombic component dominates for Ca, which receives very little electron density from the Br. More electronegative metals such as Pt and Ir receive more electron density from Br and also have lower positive charges. Therefore, the Coulomb attraction component of the binding is small, and the electron sharing component dominates. The difference in these binding mechanisms explains the trends seen in Figure 1b. The alkaline earth metals and early transition metals are more selective for water over MeBr, driven by strong Coulomb interaction between the oxygen and the metal. Moving right across the periodic table, the metals generally become more electronegative, resulting in weaker Coulomb interactions and more electron donation. This type of binding favors MeBr over water.

Figure 2: Binding energy for selected metals plotted as a function of fraction of electron donated from MeBr to the metal. The red squares indicate the contribution due to Coulomb attraction (calculated using NBO 6.0 Natural Coulomb Electrostatics analysis 51 ), and the green triangles are the total binding energy.

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Simultaneous Adsorption So far we have considered MeBr and water binding separately. Now we consider simultaneous adsorption of MeBr water for six metals: Ag, Au, Ca, Cu Ir, and Pt. These metals were chosen to include metals that we predict to be selective for water and for MeBr based on the single adsorbate binding energies. We compute the simultaneous binding energy by starting with the optimized catecholate-MeBr system and adding 1-3 water molecules in several positions and optimizing again. We also perform an optimization of the catecholate and only 1-3 water molecules with no MeBr. The binding energy associated with MeBr is then defined as the energy difference of an isolated MeBr and the water-catecholate system subtracted from the water-MeBr-catecholate system, with the BSSE correction applied. We also considered the case of adding MeBr to a catecholate that contains a bound water molecule; however, we found that this does not significantly change our results. For more discussion on this, see the Supporting Information (Table S5). Figure 3 shows how the MeBr binding energy changes as more water molecules are added. Based on the single adsorbate binding energy calculations discussed previously, we might expect Ir and Pt to also bind MeBr the strongest even in the presence of water. However, the binding strength of these metals drops sharply as the water molecules are added. Ca and Au have the strongest binding of MeBr in the presence of one water molecule, and when two water molecules are present the binding energy of Ca (-71 kJ/mol) is more than double that of the next highest metals (Ag and Ir are -33 kJ/mol). In fact, the binding energy of MeBr on Ca is not affected by the presence of one or two water molecules, and Ca is able to bind MeBr strongly even in the presence of water. Conversely, Pt and Ir, which have very strong binding energies for MeBr under dry conditions, are detrimentally affected by competitive adsorption with water. We note that the binding energy for MeBr on Pt with three waters is actually slightly lower than MeBr on Pt with 2 waters (-21 vs -29 kJ/mol), possibly due to some extra stabilization from hydrogen bonding between MeBr and water. However both values are significantly lower than the -117 kJ/mol binding for MeBr on Pt 9



under dry conditions.

Figure 3: Binding energy of MeBr on selected metals in the presence of 0-3 water molecules. The results in Figure 3 can be understood by examining the binding interactions with the different metals. As shown in Figures 4a and 4b, under dry conditions, the MeBr always binds parallel to the metal-O bond, with the Br near the metal and the methyl group stabilized by a weak electrostatic attraction to the oxygen atom. Figure 4c shows that when a water molecule is added to the Pt system, it binds between the catecholate oxygen and the methyl group, dislodging the MeBr molecule from its optimal binding position. However, when water is added to the Ca system, it binds on the opposite side of the Ca atom and does not disturb the MeBr (Figure 4d). Since Ca has a strong positive charge, the water is most stable on the far side from MeBr, where it can bind directly to the metal. This explains why adding one or two water molecules does not reduce the binding energy of MeBr on Ca. However, for metals with weaker Coulomb attraction, the water is actually more stable inserted between the catecholate and MeBr where it can form a hydrogen bond to the oxygen atom on the catecholate. We observe this same binding geometry in the Ag, Au, Cu, and Ir systems, which also exhibit weaker binding for MeBr in the presence of water. These results suggest that Ca might be a more effective metal than Ir and Pt to capture 10


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MeBr from humid air, which is opposite to the conclusion one would reach from looking solely at single component binding energies. However, due to the differences in the binding mechanisms of water and MeBr, Ca is able to bind both adsorbates strongly and demonstrates better resistance to humidity than the other metals. As seen in Figure 4f, MeBr binds to the top of the Ca catecholate rather than to the side in the presence of two waters. We note that this binding position for MeBr on Ca under dry conditions is also quite favorable and differs from the side position (Figure 4b) by less than 1 kJ/mol. Therefore, it is likely that MeBr may occupy either of these positions in the presence of water. We do not observe this behavior for the other metals we investigated; the MeBr prefers to bind to the side of the catecholate for all metals other than Ca even in the presence of water. When three water molecules are added, the metal atom becomes overcrowded and there is a large reduction in MeBr binding energy for all of the metals. We expect that for systems with more water molecules, the catecholate will be crowded by water and the MeBr binding energy will be low. Therefore, we did not perform calculations for more than three waters. Figure 4g shows that the water molecules push the MeBr farther away from the metal, weakening its binding. In the case of Ca, as seen in Figure 4h, the three water molecules all bind on the opposite side of the catecholate from the MeBr, but there is still a significant reduction in binding energy compared to Ca in dry conditions. While water binding is dominated by Coulomb attraction between oxygen and the metal, NBO population analysis indicates that the three water molecules donate some electron density to the Ca. The dry Ca atom carries a charge of +1.644 e and has a total of 18.331 electrons, while the Ca with three waters has a lower charge of +1.543 e and 18.457 electrons. This indicates that each water donates an average 0.034 electrons to the Ca. This electron donation from water reduces the affinity of the Ca for MeBr, resulting in the lower binding energy. The Ca-Br binding distance is also larger (3.081 Å for dry Ca compared to 3.161 Å with three waters), corresponding to the weaker binding.

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(a)

(b)

(c)

(d)

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(g)

(h)

Figure 4: Binding positions for (a) MeBr on Pt, (b) MeBr on Ca, (c) MeBr and one H2 O on Pt, (d) MeBr and one H2 O on Ca, (e) MeBr and two H2 Os on Pt, (f) MeBr and two H2 Os on Ca, (g) MeBr and three H2 Os on Pt, (h) MeBr and three H2 Os on Ca. The numbers and dashed lines indicate relevant interatomic distances in angstroms. 12


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Comparison with MeCl We also calculated the binding energy of MeCl for six selected metals using the same method and level of theory used for MeBr, including the counterpoise BSSE correction. The results for MeCl are tabulated in Table S4. As expected, MeCl follows the same general trends as MeBr. Ir and Pt bind both molecules strongly, while Cd binding is weak for both MeCl and MeBr. In most of the cases we examined (Mg, Ni, Cd, Ir, and Pt) the binding energy for MeBr is slightly stronger (2-20 kJ/mol) than MeCl on a given metal. In the case of Zn, MeCl binds stronger by 2.1 kJ/mol.

MeBr Dissociation In the case of four metals (Sc, Y, Hf, and Ta), during the geometry optimization MeBr dissociates into a single Br atom and a methyl radical, which bind to the metal atom in a tetrahedral configuration, as shown in the final position of Figure 5. This dissociation happens spontaneously during the geometry optimization of the MeBr and catecholate system. This results in very large binding energies for MeBr, reported in Table 1. Note that the binding energies shown for these four metals in Figure 1 use the most favorable binding position that does not cleave the Me-Br bond, not the values shown in Table 1. The binding energies in Table 1 are comparable to reported experimental values for bond dissociation of a methyl group bonded to Sc and Y ions (246 kJ/mol), 52,53 so we believe they are reasonable. Since this reaction is highly favorable, we studied the dissociation mechanism for the Sc catecholate in more detail. The mechanism and associated changes in Gibbs free energy are shown in Figure 5. These values were calculated at 298.15 K. Position A shows the initial position with the MeBr far away from the catecholate. The MeBr moves into the first local minimum aligned along with O-Sc bond (Position B). The first transition state occurs when the Me-Br bond is broken and Br bonds to the metal atom, creating a methyl radical (Position C). This step has a barrier of about 8.2 kJ/mol and leads to the local minimum at Position D, where the methyl radical is 2.575 Å from the Sc. There is a small barrier of 4.5 13



kJ/mol between this minimum and the second transition state (Position E), which occurs as the radical is bonding to the Sc at a distance of 2.556 Å. This last step results in a large stabilization of 81.2 kJ/mol and the final structure shown in Figure 5, Position F. Overall the reaction is very favorable: the first transition state is about 12 kJ/mol lower in energy than the initial position (infinite separation), and the barriers at both transition states are quite small. Our observation of MeBr dissociation on these metal catecholates is reminiscent of methyl iodide decomposition in silver-containing mordenite, which is used to capture radioactive iodine waste from nuclear energy production. 54,55 This separation process involves a complex mixture of gases, including water vapor, NO, NO2 , and CH3 I. The CH3 I molecule decomposes in the presence of partially reduced Ago -mordenite to form AgI nanoclusters or I2 and HI gas, while the methyl group forms a surface methoxy species that later reacts with NOx or water to form either methyl nitrite or methanol. Our observation of MeBr dissociation on certain metal catecholates suggests that these structures could potentially be applied to capture and destroy radioactive organic iodides.

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Figure 5: Reaction mechanism for MeBr binding to Sc catecholate with Gibbs energy at each position. Position A: initial configuration with MeBr and catecholate infinitely separated. Position B: first local minimum. Position C: first transition state, breaking the Me-Br bond. Position D: second local minimum. Position E: second transition state as methyl radical binds to Sc. Position F: final position with Me and Br bonded to Sc. Table 1: Binding energies for dissociative binding of MeBr to selected catecholates. Metal BE (kJ/mol) Ta -453 Hf -433 Y -281 Sc -278

Conclusion We have studied the binding of methyl bromide (MeBr) and water on metal catecholates using DFT. The mechanism for MeBr binding to the metal involves two components: Coulomb attraction between Br and the metal and also electron donation from Br to the metal. For 15



alkaline earth metals and early transition metals, the electron donation contribution is small, and the binding is dominated by Coulombic interactions. These metals are more selective for water over MeBr due to the strong electrostatic attraction. The more electronegative late transition metals such as Au, Pt, and Ir have stronger affinities for MeBr than for water due to significant electron donation from Br to the metal, which dominates the smaller electrostatic effects. These calculations based on single adsorbate molecules suggest that these late transition metals have good selectivity for MeBr over water; however, when MeBr and water are adsorbed simultaneously, the binding affinity for MeBr is greatly reduced due to the water interfering with MeBr binding. The binding affinity of Ca for MeBr is invariant in the presence of a small amount of water because the water and MeBr bind to opposite sides of the Ca atom and do not compete. This suggests that MeBr adsorption on Ca may be more resistant to low levels of humidity than other metals, such as Pt and Ir, that offer stronger binding of MeBr but are detrimentally affected by water. We also predict very large binding energies (more than 275 kJ/mol) for Sc, Y, Hf, and Ta due to the MeBr dissociating and binding to the metal separately as a Br atom and methyl radical.

Supplemental Information All calculated binding energies for MeBr, MeCl, and water, comparisons of DFT functionals and basis sets, spin multiplicities and calculated partial charges for metal catecholates, atomic coordinates, and sample input files can be found in the online supplemental information.

Author Information Corresponding Author Email: [email protected] (RQS) Phone: 1-847-467-2977

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Acknowledgments We gratefully acknowledge support of this work by the U.S. Department of Energy, Office of Science, Basic Energy Sciences (BES), under Award DE-FG02-08ER15967. This research was supported in part through the computational resources and staff contributions provided for the Quest high performance computing facility at Northwestern University which is jointly supported by the Office of the Provost, the Office for Research, and Northwestern University Information Technology.

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References (1) Porter, I.; Pizano, M.; Besri, M. UNEP report of the Technology and Economic Assessment Panel: Evaluation of 2016 critical use nominations for methyl bromide and related matters. http://ozone.unep.org/en/assessment-panels/technology-and-economicassessment-panel (accessed 11 May 2017). (2) Center for Disease Control, NIOSH Pocket Guide to Chemical Hazards. 2015. (3) Reshetenko, T. V.; Artyushkova, K.; St-Pierre, J. Spatial proton exchange membrane fuel cell performance under bromomethane poisoning. Journal of Power Sources 2017, 342, 135 – 147. (4) Zhai, Y.; Baturina, O.; Ramaker, D. E.; Farquhar, E.; St-Pierre, J.; Swider-Lyons, K. E. Bromomethane Contamination in the Cathode of Proton Exchange Membrane Fuel Cells. Electrochimica Acta 2016, 213, 482–489. (5) St-Pierre, J.; Ge, J.; Zhai, Y.; Reshetenko, T. V.; Angelo, M. PEMFC Cathode Contamination Mechanisms for Several VOCs-Acetonitrile, Acetylene, Bromomethane, IsoPropanol, Methyl Methacrylate, Naphthalene and Propene. ECS Transactions 2013, 58, 519–528. (6) Rhew, R. C.; Miller, B. R.; Weiss, R. F. Natural methyl bromide and methyl chloride emissions from coastal salt marshes. Nature 2000, 403, 292–295. (7) Weinberg, I.; Bahlmann, E.; Michaelis, W.; Seifert, R. Determination of fluxes and isotopic composition of halocarbons from seagrass meadows using a dynamic flux chamber. Atmospheric Environment 2013, 73, 34–40. (8) Drewer, J.; Heal, K. V.; Smith, K. A.; Heal, M. R. Methyl bromide emissions to the atmosphere from temperate woodland ecosystems. Global Change Biology 2008, 14, 2539–2547. 18


Page 18 of 26

Page 19 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(9) St-Pierre, J.; Zhai, Y.; Angelo, M. S. Effect of selected airborne contaminants on PEMFC performance. Journal of The Electrochemical Society 2014, 161, F280–F290. (10) Gan, J.; Megonnell, N. E.; Yates, S. R. Adsorption and catalytic decomposition of methyl bromide and methyl iodide on activated carbons. Atmospheric Environment 2001, 35, 941–947. (11) Snyder, J. D.; Leesch, J. G. Methyl bromide recovery on activated carbon with repeated adsorption and electrothermal regeneration. Industrial & Engineering Chemistry Research 2001, 40, 2925–2933. (12) Nordiko the

Quarantine reassessment

Systems, of

methyl

Submission bromide.

to

ERMA February

on 2010.

http://www.nordiko.com.au/fileadmin/pdf_reports/Website_ERMA_Submission_Feb_2010.pdf (accessed 11 May 2017). (13) Wang, Q.-p.; Gan, J.-y.; Papiernik, S.; Yates, S. Transformation and detoxification of halogenated fumigants by ammonium thiosulfate. Environmental Science & Technology 2000, 34, 3717–3721. (14) Gan, J.; Yates, S. R. Recapturing and decomposing methyl bromide in fumigation effluents. Journal of Hazardous Materials 1998, 57, 249–258. (15) Yang, Y.; Li, Y.; Walse, S. S.; Mitch, W. A. Destruction of Methyl Bromide Sorbed to Activated Carbon by Thiosulfate or Electrolysis. Environmental Science & Technology 2015, 49, 4515–4521. (16) Peterson, G. W.; Rossin, J. A.; Smith, P. B.; Wagner, G. W. Effects of water on the removal of methyl bromide using triethylene diamine impregnated carbon. Carbon 2010, 48, 81–88.

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(17) Leesch, J. G.; Knapp, G. F.; Mackey, B. E. Methyl bromide adsorption on activated carbon to control emissions from commodity fumigations. Journal of Stored Products Research 2000, 36, 65–74. (18) Petit, C.; Bandosz, T. J. Synthesis, characterization, and ammonia adsorption properties of mesoporous metal–organic framework (MIL (Fe))–graphite oxide composites: exploring the limits of materials fabrication. Advanced Functional Materials 2011, 21, 2108–2117. (19) Glover, T. G.; Peterson, G. W.; Schindler, B. J.; Britt, D.; Yaghi, O. MOF-74 building unit has a direct impact on toxic gas adsorption. Chemical Engineering Science 2011, 66, 163–170. (20) Kim, K. C.; Yu, D.; Snurr, R. Q. Computational screening of functional groups for ammonia capture in metal–organic frameworks. Langmuir 2013, 29, 1446–1456. (21) Ghosh, P.; Kim, K. C.; Snurr, R. Q. Modeling water and ammonia adsorption in hydrophobic Metal–organic frameworks: single components and mixtures. The Journal of Physical Chemistry C 2014, 118, 1102–1110. (22) Kim, K. C.; Moghadam, P. Z.; Fairen-Jimenez, D.; Snurr, R. Q. Computational Screening of Metal Catecholates for Ammonia Capture in Metal–Organic Frameworks. Industrial & Engineering Chemistry Research 2015, 54, 3257–3267. (23) Kizzie, A. C.; Wong-Foy, A. G.; Matzger, A. J. Effect of humidity on the performance of microporous coordination polymers as adsorbents for CO2 capture. Langmuir 2011, 27, 6368–6373. (24) Li, G.; Xiao, P.; Webley, P.; Zhang, J.; Singh, R.; Marshall, M. Capture of CO2 from high humidity flue gas by vacuum swing adsorption with zeolite 13X. Adsorption 2008, 14, 415–422.

20


Page 20 of 26

Page 21 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(25) Mason, J. A.; McDonald, T. M.; Bae, T.-H.; Bachman, J. E.; Sumida, K.; Dutton, J. J.; Kaye, S. S.; Long, J. R. Application of a high-throughput analyzer in evaluating solid adsorbents for post-combustion carbon capture via multicomponent adsorption of CO2 , N2 , and H2 O. Journal of the American Chemical Society 2015, 137, 4787–4803. (26) Li, P.; Chen, J.; Zhang, J.; Wang, X. Water stability and competition effects toward CO2 adsorption on metal organic frameworks. Separation & Purification Reviews 2015, 44, 19–27. (27) Li, B.; Dong, X.; Wang, H.; Ma, D.; Tan, K.; Shi, Z.; Chabal, Y. J.; Han, Y.; Li, J. Functionalized metal organic frameworks for effective capture of radioactive organic iodides. Faraday discussions 2017, 201, 47–61. (28) Jing, L.; Zhong, L.; Bing, L.; Qibin, X.; Hongxia, X. Effect of relative humidity on adsorption of formaldehyde on modified activated carbons. Chinese Journal of Chemical Engineering 2008, 16, 871–875. (29) Lodewyckx, P.; Vansant, E. Influence of humidity on adsorption capacity from the Wheeler-Jonas model for prediction of breakthrough times of water immiscible organic vapors on activated carbon beds. American Industrial Hygiene Association Journal 1999, 60, 612–617. (30) Werner, M. D. The effects of relative humidity on the vapor phase adsorption of trichloroethylene by activated carbon. The American Industrial Hygiene Association Journal 1985, 46, 585–590. (31) Bandosz, T. J.; Petit, C. On the reactive adsorption of ammonia on activated carbons modified by impregnation with inorganic compounds. Journal of Colloid and Interface Science 2009, 338, 329–345. (32) Petit, C.; Karwacki, C.; Peterson, G.; Bandosz, T. J. Interactions of ammonia with

21



the surface of microporous carbon impregnated with transition metal chlorides. The Journal of Physical Chemistry C 2007, 111, 12705–12714. (33) Bloch, W. M.; Burgun, A.; Coghlan, C. J.; Lee, R.; Coote, M. L.; Doonan, C. J.; Sumby, C. J. Capturing snapshots of post-synthetic metallation chemistry in metal– organic frameworks. Nature Chemistry 2014, 6, 906–912. (34) Li, J.-R.; Kuppler, R. J.; Zhou, H.-C. Selective gas adsorption and separation in metal– organic frameworks. Chemical Society Reviews 2009, 38, 1477–1504. (35) Bobbitt, N. S.; Mendonca, M. L.; Howarth, A. J.; Islamoglu, T.; Hupp, J. T.; Farha, O. K.; Snurr, R. Q. Metal–organic frameworks for the removal of toxic industrial chemicals and chemical warfare agents. Chemical Society Reviews 2017, 46, 3357–3385. (36) Doonan, C. J.; Morris, W.; Furukawa, H.; Yaghi, O. M. Isoreticular Metalation of Metal- Organic Frameworks. Journal of the American Chemical Society 2009, 131, 9492–9493. (37) Mondloch, J. E.; Bury, W.; Fairen-Jimenez, D.; Kwon, S.; DeMarco, E. J.; Weston, M. H.; Sarjeant, A. A.; Nguyen, S. T.; Stair, P. C.; Snurr, R. Q.; Farha, O. K.; Hupp, J. T. Vapor-phase metalation by atomic layer deposition in a metal–organic framework. Journal of the American Chemical Society 2013, 135, 10294–10297. (38) Nguyen, H. G. T.; Mao, L.; Peters, A. W.; Audu, C. O.; Brown, Z. J.; Farha, O. K.; Hupp, J. T.; Nguyen, S. T. Comparative study of titanium-functionalized UiO-66: support effect on the oxidation of cyclohexene using hydrogen peroxide. Catalysis Science & Technology 2015, 5, 4444–4451. (39) Weston, M. H.; Farha, O. K.; Hauser, B. G.; Hupp, J. T.; Nguyen, S. T. Synthesis and metalation of catechol-functionalized porous organic polymers. Chemistry of Materials 2012, 24, 1292–1296.

22


Page 22 of 26

Page 23 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(40) Fei, H.; Shin, J.; Meng, Y. S.; Adelhardt, M.; Sutter, J.; Meyer, K.; Cohen, S. M. Reusable oxidation catalysis using metal-monocatecholato species in a robust metal– organic framework. Journal of the American Chemical Society 2014, 136, 4965–4973. (41) Cohen, S. M. Postsynthetic methods for the functionalization of metal–organic frameworks. Chemical Reviews 2011, 112, 970–1000. (42) Bobbitt, N. S.; Snurr, R. Q. Ab initio screening of metal catecholates for adsorption of toxic pnictogen hydride gases. Industrial & Engineering Chemistry Research 2017, 56, 14324–14336. (43) Stoneburner, S. J.; Livermore, V.; McGreal, M. E.; Yu, D.; Vogiatzis, K. D.; Snurr, R. Q.; Gagliardi, L. Catechol-ligated transition metals: a quantum chemical study on a promising system for gas separation. The Journal of Physical Chemistry C 2017, 121, 10463–10469, Corrected in Stoneburner et al., J. Phys Chem. C, 2017, 121, 20553-20553. (44) Tsivion, E.; Veccham, S. P.; Head-Gordon, M. High-Temperature Hydrogen Storage of Multiple Molecules: Theoretical Insights from Metalated Catechols. ChemPhysChem 2017, 18, 184–188. (45) Tsivion, E.; Long, J. R.; Head-Gordon, M. Hydrogen physisorption on metal–organic framework linkers and metalated linkers: a computational study of the factors that control binding strength. Journal of the American Chemical Society 2014, 136, 17827– 17835. (46) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; 23



Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, Ã.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian09 Revision E.01. Gaussian Inc. Wallingford CT 2009. (47) Zhao, Y.; Truhlar, D. G. The M06 suite of density functionals for main group thermochemistry, thermochemical kinetics, noncovalent interactions, excited states, and transition elements: two new functionals and systematic testing of four M06-class functionals and 12 other functionals. Theoretical Chemistry Accounts 2008, 120, 215–241. (48) Kim, K. C.; Yu, D.; Snurr, R. Q. Computational screening of functional groups for ammonia capture in metal–organic frameworks. Langmuir 2013, 29, 1446–1456. (49) Boys, S.; Bernardi, F. The calculation of small molecular interactions by the differences of separate total energies. Some procedures with reduced errors. Molecular Physics 2002, 100, 65–73. (50) Glendening, E. D.; Landis, C. R.; Weinhold, F. NBO 6.0: natural bond orbital analysis program. Journal of Computational Chemistry 2013, 34, 1429–1437. (51) Weinhold, F. Discovering chemistry with natural bond orbitals; John Wiley & Sons, 2012. (52) Sunderlin, L.; Aristov, N.; Armentrout, P. B. Reaction of scandium ions with ethane. First and second hydride-scandium ion bond energies. Journal of the American Chemical Society 1987, 109, 78–89. 24


Page 24 of 26

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(53) Sunderlin, L.; Armentrout, P. B. Periodic trends in chemical reactivity. Reactions of scandium (+), yttrium (+), lanthanum (+), and lutetium (+) with methane and ethane. Journal of the American Chemical Society 1989, 111, 3845–3855. (54) Nenoff, T. M.; Rodriguez, M. A.; Soelberg, N. R.; Chapman, K. W. Silver-mordenite for radiologic gas capture from complex streams: Dual catalytic CH3 I decomposition and I confinement. Microporous and Mesoporous Materials 2014, 200, 297–303. (55) Chapman, K. W.; Chupas, P. J.; Nenoff, T. M. Radioactive iodine capture in silvercontaining mordenites through nanoscale silver iodide formation. Journal of the American Chemical Society 2010, 132, 8897–8899.

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TOC Graphic

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Competitive adsorption of methyl bromide and water on metal

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