NMR Spectroscopy Reveals Adsorbate Binding Sites in the Metal–Organic Framework UiO-66(Zr)

Nandy, Aditya; Forse, Alexander C.; Witherspoon, Velencia J.; Reimer, Jeffrey A.

doi:10.1021/acs.jpcc.7b12628

Cited by 48 publications

(62 citation statements)

References 85 publications

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“…28 This chemical shift difference may arise in part due to aromatic ring currents in the dobpdc 4− linkers. 37,38 Quantitative 13 C NMR indicates that at 1 bar only a small percentage (10-15%) of the adsorbed CO2 is physisorbed, and thus adsorption primarily occurs via chemisorption at this pressure. As expected, cross-polarization from 1 H → 13 C revealed only the resonance from chemisorbed 13 CO2, as the strong 1 H- 13 C dipole-dipole couplings necessary for efficient cross-polarization are absent for the physisorbed gas.…”

Section: Resultsmentioning

confidence: 99%

Elucidating CO2 Chemisorption in Diamine-Appended Metal–Organic Frameworks

Forse

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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Section: Resultsmentioning

confidence: 99%

Elucidating CO2 Chemisorption in Diamine-Appended Metal–Organic Frameworks

Forse

Milner²,

Lee³

et al. 2018

Preprint

Self Cite

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“…Clearly, to establish relationships between the effects of the functionalization of MOFs on their sorption capacities results a very difficult task, because there are numerous factors to consider [ 37 ]. Among them, pore size reduction and molecular sieving effect [ 38 ], changes in polar character or electronic environments of the frameworks, energy effects [ 39 ] or other factors (such as intrinsic defects, co-adsorption, or diffusive transport in the material pores, as those most remarkable).…”

Section: Resultsmentioning

confidence: 99%

Influence of Ligand Functionalization of UiO-66-Based Metal-Organic Frameworks When Used as Sorbents in Dispersive Solid-Phase Analytical Microextraction for Different Aqueous Organic Pollutants

et al. 2018

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Four metal-organic frameworks (MOFs), specifically UiO-66, UiO-66-NH2, UiO-66-NO2, and MIL-53(Al), were synthesized, characterized, and used as sorbents in a dispersive micro-solid phase extraction (D-µSPE) method for the determination of nine pollutants of different nature, including drugs, phenols, polycyclic aromatic hydrocarbons, and personal care products in environmental waters. The D-µSPE method, using these MOFs as sorbents and in combination with high-performance liquid chromatography (HPLC) and diode-array detection (DAD), was optimized. The optimization study pointed out to UiO-66-NO2 as the best MOF to use in the multi-component determination. Furthermore, the utilization of isoreticular MOFs based on UiO-66 with the same topology but different functional groups, and MIL-53(Al) to compare with, allowed us for the first time to evaluate the influence of such functionalization of the ligand with regards to the efficiency of the D-µSPE-HPLC-DAD method. Optimum conditions included: 20 mg of UiO-66-NO2 MOF in 20 mL of the aqueous sample, 3 min of agitation by vortex and 5 min of centrifugation, followed by the use of only 500 µL of acetonitrile as desorption solvent (once the MOF containing analytes was separated), 5 min of vortex and 5 min of centrifugation. The validation of the D-µSPE-HPLC-DAD method showed limits of detection down to 1.5 ng·L−1, average relative recoveries of 107% for a spiked level of 1.50 µg·L−1, and inter-day precision values with relative standard deviations lower than 14%, for the group of pollutants considered.

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“…To eliminate the background signal from the NMR probe, we used both spin-echo (90°τ -180°-τ-acquire) and one-pulse sequence measurements to record the 1 H spectra. 52 A radiofrequency field strength (B 1 ) of 60 kHz and a spin-echo delay of τ = 119 μ s were used, while using a recycle delay of 1 s. 1 H two-dimensional homonuclear exchange experiments were performed on samples with VOC loadings where additional peaks (relative to the neat VOCs) emerged. 53 Mixing times in the range of 0.001, 0.1, and 0.25 s were used.…”

Section: Nmr Experimentsmentioning

confidence: 99%

Revealing Molecular Mechanisms in Hierarchical Nanoporous Carbon via Nuclear Magnetic Resonance

Mao

Tang

et al. 2020

Matter

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Hierarchical nanoporous carbons (HNC) have been proven to be an effective adsorbent for the adsorption of volatile organic compounds (VOCs) and CO 2 . , However,althoughHowever , questions remain regarding the hierarchical structure regulation, the adsorption mechanisms of adsorbate uptake, and interactions within the HNC. We synthesize HNC from wood, using a microwave-induced heating method incorporating K 2 CO 3 activation. Our HNC. HNCOOUr exhibit Murray's law multiscale structures, prompting a molecular-scale study of adsorbate adsorption via nuclear magnetic resonance (NMR). NMR chemical shifts are consistent with ring-current effects from the adsorbent. Our NMR technique provides a convenient way to quantitate adsorption of adsorbate in HNC. VOC vapor adsorption results show NMR chemical-shift changes with time, suggesting initial adsorption into mesopores, followed by diffusion into micropores.Schroeder's paradox is demonstrated by differences in observed shifts for adsorbed liquid vis-à-vis vapor phase in these HNC. These HNC show high CO 2 adsorption capacity, portending applications to carbon capture.

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NMR Spectroscopy Reveals Adsorbate Binding Sites in the Metal–Organic Framework UiO-66(Zr)

Cited by 48 publications

References 85 publications

Elucidating CO2 Chemisorption in Diamine-Appended Metal–Organic Frameworks

Elucidating CO2 Chemisorption in Diamine-Appended Metal–Organic Frameworks

Influence of Ligand Functionalization of UiO-66-Based Metal-Organic Frameworks When Used as Sorbents in Dispersive Solid-Phase Analytical Microextraction for Different Aqueous Organic Pollutants

Revealing Molecular Mechanisms in Hierarchical Nanoporous Carbon via Nuclear Magnetic Resonance

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