Overcoming double-step CO<sub>2</sub> adsorption and minimizing water co-adsorption in bulky diamine-appended variants of Mg<sub>2</sub>(dobpdc)

Milner, Phillip J.; Martell, Jeffrey D.; Siegelman, Rebecca L.; Gygi, David; Weston, Simon C.; Long, Jeffrey R.

doi:10.1039/c7sc04266c

“…Indeed, NMR characterization of dmpn-Mg2(dotpdc) ( Figure 9b,c) revealed a complex mixture of ammonium carbamate and carbamic acid species, quantified overall in a 1:0.5 ratio, respectively, rather than the 1:1 mixed structure observed for dmpn-Mg2(dobpdc). We note that sharp CO2 adsorption isotherm steps have been observed previously for a range of diamine-appended M2(dotpdc) variants, including nPr-2-Mg2(dotpdc) (nPr-2 = Npropylethylenediamine), 16 indicating that such materials are capable of cooperative adsorption by ammonium carbamate chain formation. Indeed, NMR measurements of nPr-2-Mg2(dotpdc) were fully consistent with the exclusive formation of ammonium carbamate chains ( Figure S18).…”

Section: Resultssupporting

confidence: 76%

Elucidating CO₂ Chemisorption in Diamine-Appended Metal–Organic Frameworks

Forse¹,

Milner

²

,

Lee

³

et al. 2018

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The widespread deployment of carbon capture and sequestration as a climate change mitigation strategy could be facilitated by the development of more energy-efficient adsorbents. Diamine-appended metal-organic frameworks of the type diamine-M2(dobpdc) (M = Mg, Mn, Fe, Co, Ni, Zn; dobpdc 4− = 4,4′-dioxidobiphenyl-3,3′-dicarboxylate) have shown promise for carbon capture applications, although questions remain regarding the molecular mechanisms of CO2 uptake in these materials. Here, we leverage the crystallinity and tunability of this class of frameworks to perform a comprehensive study of CO2 chemisorption. Using multinuclear nuclear magnetic resonance (NMR) spectroscopy experiments and van der Waals-corrected density functional theory (DFT) calculations for thirteen diamine-M2(dobpdc) variants, we demonstrate that the canonical CO2 chemisorption products-ammonium carbamate chains and carbamic acid pairs-can be readily distinguished, and that ammonium carbamate chain formation dominates for diamine-Mg2(dobpdc) materials. In addition, we elucidate a new chemisorption mechanism in the material dmpn-Mg2(dobpdc) (dmpn = 2,2-dimethyl-1,3-diaminopropane), which involves formation of a 1:1 mixture of ammonium carbamate and carbamic acid and accounts for the unusual adsorption properties of this material. Finally, we show that the presence of water plays an important role in directing the mechanisms for CO2 uptake in diamine-M2(dobpdc) materials. Overall, our combined NMR and DFT approach enables a thorough depiction and understanding of CO2 adsorption within diamine-M2(dobpdc) compounds, which may aid similar studies in other amine-functionalized adsorbents in the future. Structure files generated by DFT calculations with the PBE functional and the D3 vdW correction (CIF).

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“…54 Importantly, the distance between metal centers along the c axis is anticipated to be very similar in both frameworks. 16 The CO2 adsorption profile of dmpn-Mg2(dotpdc) is broad compared to that of dmpn-Mg2(dobpdc), which suggests a primarily non-cooperative adsorption mechanism (Figure 9a). Indeed, NMR characterization of dmpn-Mg2(dotpdc) (Figure 9b,c) revealed a complex mixture of ammonium carbamate and carbamic acid species, quantified overall in a 1:0.5 ratio, respectively, rather than the 1:1 mixed structure observed for dmpn-Mg2(dobpdc).…”

Section: Compoundmentioning

confidence: 99%

Elucidating CO2 Chemisorption in Diamine-Appended Metal–Organic Frameworks

Forse

¹

,

Milner²,

Lee³

et al. 2018

Preprint

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The widespread deployment of carbon capture and sequestration as a climate change mitigation strategy could be facilitated by the development of more energy-efficient adsorbents. Diamine-appended metal-organic frameworks of the type diamine-M2(dobpdc) (M = Mg, Mn, Fe, Co, Ni, Zn; dobpdc 4− = 4,4′-dioxidobiphenyl-3,3′-dicarboxylate) have shown promise for carbon capture applications, although questions remain regarding the molecular mechanisms of CO2 uptake in these materials. Here, we leverage the crystallinity and tunability of this class of frameworks to perform a comprehensive study of CO2 chemisorption. Using multinuclear nuclear magnetic resonance (NMR) spectroscopy experiments and van der Waals-corrected density functional theory (DFT) calculations for thirteen diamine-M2(dobpdc) variants, we demonstrate that the canonical CO2 chemisorption products-ammonium carbamate chains and carbamic acid pairs-can be readily distinguished, and that ammonium carbamate chain formation dominates for diamine-Mg2(dobpdc) materials. In addition, we elucidate a new chemisorption mechanism in the material dmpn-Mg2(dobpdc) (dmpn = 2,2-dimethyl-1,3-diaminopropane), which involves formation of a 1:1 mixture of ammonium carbamate and carbamic acid and accounts for the unusual adsorption properties of this material. Finally, we show that the presence of water plays an important role in directing the mechanisms for CO2 uptake in diamine-M2(dobpdc) materials. Overall, our combined NMR and DFT approach enables a thorough depiction and understanding of CO2 adsorption within diamine-M2(dobpdc) compounds, which may aid similar studies in other amine-functionalized adsorbents in the future.

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“…Furthermore, increased H 2 O co‐adsorption in the presence of humidity is observed. MOFs with either a more uniformly hexagonal pore structure or longer organic linkers seem to do not suffer from these drawbacks . Nonetheless, larger diamines reduce the surface areas of the MOF, decreasing the gravimetric CO 2 uptake capacities.…”

Section: Introductionmentioning

confidence: 99%

Strategies to Enhance Carbon Dioxide Capture in Metal‐Organic Frameworks

Piscopo

¹

,

Loebbecke

²

2020

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The dramatic increase of atmospheric CO2 concentration is responsible for a fast and potentially unpredictable global climate change. Therefore, the implementation of negative carbon technologies such as direct air capture (DAC) is needed. Metal–organic frameworks (MOFs) have the potential to perform CO2 DAC and achieve unprecedented performances. Herein strategies to improve the CO2 capture efficiency of MOFs and their potential implementation in real applications are discussed. Three main categories of targeted modifications to the frameworks are usually performed to enhance the CO2 uptake capacity and adsorption selectivity: 1) modifications to the metal unit; 2) modifications to the linker unit; 3) confinement of solvents within MOFs. The synthesis of MOF composites using other porous materials as support is also a useful method to improve the CO2 capture performances. Another approach involves the synthesis of amine‐functionalized MOFs that can chemically bind carbon dioxide.

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Overcoming double-step CO₂ adsorption and minimizing water co-adsorption in bulky diamine-appended variants of Mg₂(dobpdc)

Abstract: Judicious choice of framework structure allows for single CO2 adsorption steps with bulky primary,secondary diamines appended to metal–organic frameworks.

Cited by 92 publications

References 77 publications

Elucidating CO₂ Chemisorption in Diamine-Appended Metal–Organic Frameworks

Elucidating CO₂ Chemisorption in Diamine-Appended Metal–Organic Frameworks

Elucidating CO2 Chemisorption in Diamine-Appended Metal–Organic Frameworks

Strategies to Enhance Carbon Dioxide Capture in Metal‐Organic Frameworks

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Overcoming double-step CO2 adsorption and minimizing water co-adsorption in bulky diamine-appended variants of Mg2(dobpdc)

Abstract: Judicious choice of framework structure allows for single CO2 adsorption steps with bulky primary,secondary diamines appended to metal–organic frameworks.

Cited by 92 publications

References 77 publications

Elucidating CO2 Chemisorption in Diamine-Appended Metal–Organic Frameworks

Elucidating CO2 Chemisorption in Diamine-Appended Metal–Organic Frameworks

Elucidating CO2 Chemisorption in Diamine-Appended Metal–Organic Frameworks

Strategies to Enhance Carbon Dioxide Capture in Metal‐Organic Frameworks

Contact Info

Product

Resources

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Overcoming double-step CO₂ adsorption and minimizing water co-adsorption in bulky diamine-appended variants of Mg₂(dobpdc)

Elucidating CO₂ Chemisorption in Diamine-Appended Metal–Organic Frameworks

Elucidating CO₂ Chemisorption in Diamine-Appended Metal–Organic Frameworks