Research ArticleChemistry

Hypergolic zeolitic imidazolate frameworks (ZIFs) as next-generation solid fuels: Unlocking the latent energetic behavior of ZIFs

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Science Advances  05 Apr 2019:
Vol. 5, no. 4, eaav9044
DOI: 10.1126/sciadv.aav9044
  • Fig. 1 The design and molecules used herein for the development of hypergolic ZIFs.

    (A) Similarity between the organic linker in a ZIF (top) and a typical energetic imidazolium cation (bottom). (B) The ligands HAIm and HVIm used in the development of hypergolic ZIFs.

  • Fig. 2 Structural analysis and hypergolic properties of hypergolic ZIFs.

    (A) Final Rietveld fits for Zn(AIm)2, Co(AIm)2, and Cd(AIm)2 (top row) and for Zn(VIm)2, Co(VIm)2, and Cd(VIm)2 (bottom row). (B) Examples of hypergolicity drop tests for HAIm, Zn(AIm)2, Co(AIm)2, and Cd(AIm)2 (top row) and for HVIm, Zn(VIm)2, Co(VIm)2, and Cd(VIm)2 (bottom row). The moment of ignition for each experiment is indicated by a red star. Each drop test was conducted in triplicate (see Table 1). Photo credit: Hatem M. Titi, McGill University.

  • Table 1 Hypergolic properties of herein explored ZIFs and corresponding ligands in drop tests using WFNA and RFNA as oxidizers.

    Each test was conducted in triplicate.

    FuelDrop test with WFNADrop test with RFNA
    ID (ms)Flame
    duration (ms)
    Flame
    height* (cm)
    Flame colorID (ms)Flame
    duration (ms)
    Flame
    height* (cm)
    Flame color
    Zn(AIm)22(1), 4(1)>6004Red, blue12(2)<1504Red, blue
    Co(AIm)22(1), 2(1)>2004Orange7(2), 10(2)>2005Orange
    Cd(AIm)25(1), 3(2)>2006Yellow30(2)<1504Orange
    Zn(VIm)229(1)SparksSparksRedSmoke
    Co(VIm)211(5)>2002Orange164§SparksOrange
    Cd(VIm)235(1)SparksSparksYellowSmoke
    ZIF-8
    Zn(EtIm)2
    HAIm34(4)>1007RedSmoke
    HVIm34(2)SparksSparksRedSmoke

    *Approximate values.

    †Sample made from solution.

    ‡No ignition.

    §Ignited in only one of three tests.

    ‖RHO topology framework.

    • Table 2 Calculated combustion energy ΔEc, gravimetric (Eg) and volumetric (EV) energy density, and crystallographic unit cell parameter (a) for ZIFs.

      ZIFΔEc/kJ mol−1Eg/kJ g−1EV/kJ cm−3a
      Zn(AIm)2−4783.819.319.317.045(1)
      Co(AIm)2−4760.019.719.516.960(2)
      Cd(AIm)2−4799.916.316.517.9721(9)
      Zn(VIm)2−4789.919.018.917.147(2)*
      Co(VIm)2−4767.619.518.417.296(1)
      Cd(VIm)2−4808.416.115.818.234(2)
      ZIF-8−3916.017.215.9§16.992(1)

      *From CSD structure GAZBOB (28).

      †Measured enthalpy of combustion (ΔHc) is −4649.0 kJ mol−1.

      ‡20.6 kJ g−1 based on measured ΔHc.

      §18.9 kJ cm−3 based on measured ΔHc.

      ‖CSD structure OFERUN02 (27).

      Supplementary Materials

      • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/4/eaav9044/DC1

        Fig. S1. Reaction scheme for the synthesis of HAIm.

        Fig. S2. NMR spectra for the ligand HAIm.

        Fig. S3. Overlay of PXRD patterns of mechanochemically prepared ZIFs immediately after milling, compared to the simulated pattern for ZIF-8.

        Fig. S4. Thermal analysis data for acetylene-substituted MOFs.

        Fig. S5. Thermal analysis data for vinyl-substituted MOFs.

        Fig. S6. Overlay of selected FTIR-ATR spectra.

        Fig. S7. Selected solid-state NMR spectra.

        Fig. S8. Comparison of PXRD patterns for selected MOFs after impact testing.

        Fig. S9. Selected images of hypergolic drop tests on hypergolic ZIFs using RFNA oxidizer.

        Fig. S10. Nitrogen desorption and adsorption curves for selected MOFs.

        Fig. S11. Thermogravimetric analysis of ZIFs with included nitromethane guest.

        Fig. S12. Selected examples of hypergolic drop tests on ZIFs containing guests.

        Fig. S13. Calculated DOS plots for the herein studied frameworks.

        Fig. S14. The hypergolicity of selected ZIFs after 1 month using WFNA as an oxidizer.

        Fig. S15. Illustration of vinyl-substituent disorder in the structure of SOD-Co(VIm)2.

        Table S1. Summary of crystallographic and Rietveld refinement parameters.

        Table S2. Reaction equations used in the calculation of combustion energies.

        Table S3. Calculated bandgaps for herein studied ZIF structures.

        Data file S1. Crystallographic data (in CIF format) for crystal structures of ZIF materials.

        Data file S2. CheckCIF (in PDF format) for crystal structures of ZIF materials.

        Data file S3. Movie (in MOV format) of an example drop test conducted using Co(AIm)2, with WFNA as the oxidizer.

      • Supplementary Materials

        The PDF file includes:

        • Fig. S1. Reaction scheme for the synthesis of HAIm.
        • Fig. S2. NMR spectra for the ligand HAIm.
        • Fig. S3. Overlay of PXRD patterns of mechanochemically prepared ZIFs immediately after milling, compared to the simulated pattern for ZIF-8.
        • Fig. S4. Thermal analysis data for acetylene-substituted MOFs.
        • Fig. S5. Thermal analysis data for vinyl-substituted MOFs.
        • Fig. S6. Overlay of selected FTIR-ATR spectra.
        • Fig. S7. Selected solid-state NMR spectra.
        • Fig. S8. Comparison of PXRD patterns for selected MOFs after impact testing.
        • Fig. S9. Selected images of hypergolic drop tests on hypergolic ZIFs using RFNA oxidizer.
        • Fig. S10. Nitrogen desorption and adsorption curves for selected MOFs.
        • Fig. S11. Thermogravimetric analysis of ZIFs with included nitromethane guest.
        • Fig. S12. Selected examples of hypergolic drop tests on ZIFs containing guests.
        • Fig. S13. Calculated DOS plots for the herein studied frameworks.
        • Fig. S14. The hypergolicity of selected ZIFs after 1 month using WFNA as an oxidizer.
        • Fig. S15. Illustration of vinyl-substituent disorder in the structure of SOD-Co(VIm)2.
        • Table S1. Summary of crystallographic and Rietveld refinement parameters.
        • Table S2. Reaction equations used in the calculation of combustion energies.
        • Table S3. Calculated bandgaps for herein studied ZIF structures.
        • Legends for Data file S1 to S3

        Download PDF

        Other Supplementary Material for this manuscript includes the following:

        • Data file S1. Crystallographic data (in CIF format) for crystal structures of ZIF materials.
        • Data file S2. CheckCIF (in PDF format) for crystal structures of ZIF materials.
        • Data file S3. Movie (in MOV format) of an example drop test conducted using Co(AIm)2, with WFNA as the oxidizer.

        Files in this Data Supplement:

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