Research ArticleChemistry

A single-ligand ultra-microporous MOF for precombustion CO2 capture and hydrogen purification

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Science Advances  18 Dec 2015:
Vol. 1, no. 11, e1500421
DOI: 10.1126/sciadv.1500421
  • Fig. 1 Nanoporous structure of 1.

    (A) Single-crystal x-ray structure of 1 generated using OLEX; green, Ni dimers reduced to one node. The green cones trace the six-connected distorted cubic arrangement formed by collapsing the Ni dimers to nodes and the PyC linkers as lines. The yellow ball represents the cages in the structure. (B) The Connolly surface diagram of 1 (probe radius, 1.4 Å) showing the 2D and 1D channels. The channels labeled I and III are interconnected and run along the a and c axes, respectively, whereas the channel labeled II is truly one-dimensional along the c axis. IV represents the cages in 1, which are lined with terminal water molecules in addition to the ligand groups.

  • Fig. 2 Experimental and simulated adsorption isotherms and HOA plots.

    (A) Experimental H2 and N2 isotherms. (B) CO2 adsorption isotherms carried out on 1 at different temperatures (filled circles, adsorption; open circles, desorption). For CO2 at 195 K, the simulated adsorption isotherm is shown. (C) HOA for CO2 in 1 as a function of the CO2 loading determined from a virial fit to isotherms collected at temperatures ranging from −25° to 30°C. HOA determined from GCMC simulations at 25°C are also shown. (D) Experimental and simulated gas adsorption isotherms for CO2 at 298 K (0 to 10 bar).

  • Fig. 3 CO2 binding sites modeled from simulations.

    (A) A view looking down the c axis of 1 showing the top 30 CO2 binding sites determined from a GCMC simulation at 195 K and 1 bar. There are three distinct binding regions noted in blue (I/III), green (II), and red (IV). Binding region I/III corresponds to the 2D channels depicted in Fig. 1B. Binding region II corresponds to the 1D channels labeled II in Fig. 1B. IV corresponds to the near-spherical cage. (B to D) Close-ups and different views of binding regions. (B) I/III. (C) II. (D) IV.

  • Fig. 4 Working capacities and selectivity characteristics.

    (A and B) The working capacity of 1 determined from simulation compared to that of several industrial sorbents and MOFs determined from (i) 80H2/20CO2 and (ii) 60H2/40CO2 gas mixtures at 313 K. The working capacities have been evaluated using a desorption pressure of 1 bar. (C and D) Comparison of the H2/CO2 selectivity of 1 versus other known MOFs and industrial sorbents determined from (i) 80H2/20CO2 and (ii) 60H2/40CO2 gas mixtures at 313 K. Data for activated carbon JX101, zeolite 13X, MgMOF-74, and Cu-BTTri are taken from the study of Herm et al. (23).

  • Fig. 5 Stability and CO2 self-diffusion kinetics.

    (A) PXRDs showing the hydrolytic, hydrostatic stabilities and the homogeneity of the milligram- and gram-scale syntheses of 1. (B) CO2 adsorption isotherms of 1 at 273 K for as made and following exposure to humid (30% RH) CO2 for 48 hours (filled circles, adsorption; open circles, desorption). (C) TGA cycling data on 1 carried out at 308 K. Blue, CO2 flow; red, N2 flow. DSC, differential scanning calorimetry. (D) Diffusion coefficient (Dc) as a function of CO2 loading from eight loadings at 273 K for both the powder and pelletized forms of 1. Average diffusion coefficients for the powder and the pellet are 3.03 × 10−9 and 1.66 × 10−9 m2 s−1, respectively.

  • Fig. 6 Breakthrough measurements for CO2-H2 mix.

    (A) Breakthrough curve for the 60% H2/40% CO2 binary component mixture measured at 298 K and 1 bar. (B) Breakthrough curve for the 60% He/40% CO2 binary component mixture measured at 298 K and 1 bar. T1 and T2 represent the bed temperatures measured at two points along the column (adsorption front).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/1/11/e1500421/DC1

    Materials and Methods

    Single-crystal structure determination

    Analytical characterizations

    Adsorption analysis

    Pore size determination from PALS

    Virial

    Simulation results: HOA, selectivities, and working capacities

    Stability studies

    Adsorption-desorption cycling experiments

    Self-diffusion coefficient CO2 in 1

    Computational and molecular modeling details

    Comparison of CO2/H2 selectivities of MOFs reported in the literature

    Fig. S1. Comparison of the nickel clusters present in 1, with the recently reported nickel clusters in pyridine carboxylate–based MOFs.

    Fig. S2. Connolly surface representations of the nanoporous channels.

    Fig. S3. PXRD of 1, simulated versus as synthesized (milligram and gram scale).

    Figs. S4 and S5. TGA of the as-made sample and the activated sample.

    Fig. S6. Infrared spectra of 1.

    Fig. S7. CO2 and N2 adsorption isotherms of the milligram- and gram-scale syntheses.

    Fig. S8. Fitting comparison obtained for the nonlocal DFT fit to the 195-K CO2 data.

    Fig. S9. Langmuir fits from the 195-K CO2 data.

    Fig. S10. BET and Langmuir fits from the 77-K N2 data.

    Fig. S11. Pore size distribution obtained from nonlocal DFT fit.

    Fig. S12. PALS spectra of 1 at room temperature before and after the thermal annealing.

    Fig. S13. HOA plots obtained from the virial fits and DFT analysis of the CO2 isotherms.

    Fig. S14. Comparison of experimental isotherms to the ones obtained from virial fits.

    Fig. S15. Virial plots carried out using CO2 isotherms at different temperatures.

    Fig. S16. High-pressure H2 isotherm at 298 K.

    Fig. S17. Simulated HOA plots.

    Fig. S18. CO2/H2 selectivity from ideal adsorbed solution theory.

    Fig. S19. Pure-component working capacity.

    Fig. S20. Simulated mixed-component isotherm for H2 purification and precombustion gas mixture.

    Figs. S21 and S22. Mixed-component working capacities for a PSA (10 to 1 bar).

    Figs. S23 and S24. Hydrolytic and thermal stability of 1 from PXRD.

    Fig. S25. Hydrolytic stability evaluated from water vapor adsorption measurements.

    Fig. S26. Hydrolytic stability from gas adsorption studies.

    Fig. S27. Hydrolytic stability of 1 exposed to 80% RH at 80°C for 48 hours.

    Fig. S28. Pressure-induced amorphization test from both PXRD and gas adsorption isotherms.

    Fig. S29. Shelf life of 1 from gas adsorption isotherms.

    Fig. S30. Comparison of the TGA cycling data for CO2-N2 cycling done on 1 and ZnAtzOx at 35°C.

    Fig. S31. Modeling of diffusion kinetics of CO2 in 1 from experiment and simulation.

    Fig. S32. Plot of the mean square displacement of CO2 from a molecular dynamics simulation for which a computed diffusion coefficient was estimated.

    Fig. S33. A graphical representation of the solvent-accessible volume of 1.

    Fig. S34. Snapshots from an MD simulation of CO2 diffusing from the cage to the channels.

    Fig. S35. Comparison of the probability densities of CO2 derived from GCMC simulations at 195 K and 1 bar and 298 K and 40 bar.

    Table S1. CO2 uptakes at 195 and 273 K for selected ultra- and microporous MOFs.

    Table S2. CO2 adsorption and desorption data at 195 K.

    Table S3. Fitting results of 1 from PALS analysis.

    Table S4. Summary of the fitted virial parameters.

    Table S5. Uptakes and selectivities for the binary CO2/H2 (40:60) precombustion gas mixtures at a range of pressures.

    Table S6. Uptakes and selectivities for the binary CO2/H2 (20:80) H2 purification mixture at a range of pressures.

    Table S7. Working capacities and selectivities for a PSA (10 to 1 bar) at 313 K at the relevant H2/CO2 gas mixtures for H2 purification (80:20) and precombustion CO2 capture (60:40) for integrated gasification combined cycle systems.

    Table S8. Force field parameters used to model the H2 guest molecules.

    Table S9. Lennard-Jones parameters for framework atoms from the universal force field, CO2 guest molecules.

    Table S10. Cooperative CO2-CO2 energies with respect to the number of molecules loaded.

    Table S11. H2/CO2 selectivities from literature.

  • Supplementary Materials

    This PDF file includes:

    • Materials and Methods
    • Single-crystal structure determination
    • Fig. S1. Comparison of the nickel clusters present in 1, with the recently reported nickel clusters in pyridine carboxylate–based MOFs.
    • Fig. S2. Connolly surface representations of the nanoporous channels.
    • Table S1. CO2 uptakes at 195 and 273 K for selected ultra- and microporous MOFs.
    • Analytical characterizations
    • Fig. S3. PXRD of 1, simulated versus as synthesized (milligram and gram scale).
    • Figs. S4 and S5. TGA of the as-made sample and the activated sample.
    • Fig. S6. Infrared spectra of 1.
    • Adsorption analysis
    • Table S2. CO2 adsorption and desorption data at 195 K.
    • Fig. S7. CO2 and N2 adsorption isotherms of the milligram- and gram-scale syntheses.
    • Fig. S8. Fitting comparison obtained for the nonlocal DFT fit to the 195-K CO2 data.
    • Fig. S9. Langmuir fits from the 195-K CO2 data.
    • Fig. S10. BET and Langmuir fits from the 77-K N2 data.
    • Fig. S11. Pore size distribution obtained from nonlocal DFT fit.
    • Pore size determination from PALS
    • Table S3. Fitting results of 1 from PALS analysis.
    • Fig. S12. PALS spectra of 1 at room temperature before and after the thermal annealing.
    • Virial
    • Table S4. Summary of the fitted virial parameters.
    • Fig. S13. HOA plots obtained from the virial fits and DFT analysis of the CO2 isotherms.
    • Fig. S14. Comparison of experimental isotherms to the ones obtained from virial fits.
    • Fig. S15. Virial plots carried out using CO2 isotherms at different temperatures.
    • Fig. S16. High-pressure H2 isotherm at 298 K.
    • Simulation results: HOA, selectivities, and working capacities
    • Fig. S17. Simulated HOA plots.
    • Fig. S18. CO2/H2 selectivity from ideal adsorbed solution theory.
    • Table S5. Uptakes and selectivities for the binary CO2/H2 (40:60) precombustion gas mixtures at a range of pressures.
    • Table S6. Uptakes and selectivities for the binary CO2/H2 (20:80) H2 purification mixture at a range of pressures.
    • Table S7. Working capacities and selectivities for a PSA (10 to 1 bar) at 313 K at the relevant H2/CO2 gas mixtures for H2 purification (80:20) and precombustion CO2 capture (60:40) for integrated gasification combined cycle systems.
    • Fig. S19. Pure-component working capacity.
    • Fig. S20. Simulated mixed-component isotherm for H2 purification and precombustion gas mixture.
    • Figs. S21 and S22. Mixed-component working capacities for a PSA (10 to 1 bar).
    • Stability studies
    • Figs. S23 and S24. Hydrolytic and thermal stability of 1 from PXRD.
    • Fig. S25. Hydrolytic stability evaluated from water vapor adsorption measurements.
    • Fig. S26. Hydrolytic stability from gas adsorption studies.
    • Fig. S27. Hydrolytic stability of 1 exposed to 80% RH at 80°C for 48 hours.
    • Fig. S28. Pressure-induced amorphization test from both PXRD and gas adsorption isotherms.
    • Fig. S29. Shelf life of 1 from gas adsorption isotherms.
    • Adsorption-desorption cycling experiments
    • Fig. S30. Comparison of the TGA cycling data for CO2-N2 cycling done on 1 and ZnAtzOx at 35°C.
    • Self-diffusion coefficient CO2 in 1
    • Fig. S31. Modeling of diffusion kinetics of CO2 in 1 from experiment and simulation.
    • Computational and molecular modeling details
    • Table S8. Force field parameters used to model the H2 guest molecules.
    • Table S9. Lennard-Jones parameters for framework atoms from the universal force field, CO2 guest molecules.
    • Table S10. Cooperative CO2-CO2 energies with respect to the number of molecules loaded.
    • Fig. S32. Plot of the mean square displacement of CO2 from a molecular dynamics simulation for which a computed diffusion coefficient was estimated.
    • Fig. S33. A graphical representation of the solvent-accessible volume of 1.
    • Fig. S34. Snapshots from an MD simulation of CO2 diffusing from the cage to the channels.
    • Fig. S35. Comparison of the probability densities of CO2 derived from GCMC simulations at 195 K and 1 bar and 298 K and 40 bar.
    • Comparison of CO2/H2 selectivities of MOFs reported in the literature
    • Table S11. H2/CO2 selectivities from literature.

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