Skip to main content
  • Brief Communication: Nano and macroporous materials (aerogels, xerogels, cryogels, etc.)
  • Published:

Synthesis of hierarchically porous MgO monoliths with continuous structure via sol–gel process accompanied by phase separation

Abstract

Hierarchically porous magnesium oxide, MgO, monoliths with a well-defined continuous macroporous structure have been synthesized via the sol–gel route accompanied by phase separation. Magnesium chloride hexahydrate was used as a precursor, and propylene oxide was used as an acid scavenger to raise the pH of a reaction solution homogenously. In order to obtain a crack-free monolith after heating in air, poly(vinylpyrrolidone), PVP, was employed as a scaffold of the skeleton as well as a phase separation controller to form the continuous macropores with higher homogeneity. Due to the moderate hydrogen-bonding interaction with magnesium hydroxide, PVP reinforces the gel network essentially composed of fine grained magnesium hydroxide. Even after the removal of all organic components by calcination, the porous gel samples maintained their monolithic form. On the other hand, an additional incorporation of 1,3,5-benzenetricarboxylic acid, H3BTC, was found to be effective in suppressing the oriented growth of the micrometer-sized crystalline phase. The polycrystalline MgO monoliths with specific surface area of 185, 64, and 48 m2 g−1 were prepared after heating at 400, 500, and 600 °C in air, respectively.

Appearances (upper) and SEM images(lower) of monolithic MgO-based gel before and after heat-treatment.

This is a preview of subscription content, access via your institution.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8

References

  1. 1.

    Shi L, Chu Z, Liu Y, Jin W, Xu N (2014) In situ fabrication of three-dimensional graphene films on gold substrates with controllable pore structures for high-performance electrochemical sensing. Adv Funct Mater 24:7032–7041

    Article  Google Scholar 

  2. 2.

    Collins G, Blomker M, Osiak M, Holmes JD, Bredol M, O’Dwyer C (2013) Three-dimensionally ordered hierarchically porous tin dioxide inverse opals and immobilization of palladium nanoparticles for catalytic applications. Chem Mater 25:4312–4320

    Article  Google Scholar 

  3. 3.

    Tanaka N, Nagayama H, Kobayashi H, Ikegami T, Hosoya K, Ishizuka N, Lubda D (2000) Monolithic silica columns for HPLC, micro-HPLC, and CEC. J Sep Sci 23:111–116

    Google Scholar 

  4. 4.

    Srinivas G, Krungleviciute V, Guo ZX, Yildirim T (2014) Exceptional CO2 capture in a hierarchically porous carbon with simultaneous high surface area and pore volume. Energy Environ Sci 7:335–342

    Article  Google Scholar 

  5. 5.

    Nakanishi K, Soga N (1991) Phase separation in gelling silica-organic polymer solution: systems containing poly (sodium styrenesulfonate). J Am Ceram Soc 74:2518–2530

    Article  Google Scholar 

  6. 6.

    Flory PJ (1942) Thermodynamics of high polymer solutions. J Chem Phys 10:51–61

    Article  Google Scholar 

  7. 7.

    Huggins ML (1942) Some properties of solutions of long-chain compounds. J Phys Chem 46:151–158

    Article  Google Scholar 

  8. 8.

    Konishi J, Fujita K, Nakanishi K, Hirao K (2006) Monolithic TiO2 with controlled multiscale porosity via a template-free sol-gel process accompanied by phase separation. Chem Mater 18:6069–6074

    Article  Google Scholar 

  9. 9.

    Hasegawa G, Kanamori K, Nakanishi K, Hanada T (2010) Facile preparation of hierarchically porous TiO2 monoliths. J Am Ceram Soc 93:3110–3115

    Article  Google Scholar 

  10. 10.

    Konishi J, Fujita K, Oiwa S, Nakanishi K, Hirao K (2008) Crystalline ZrO2 monoliths with well-defined macropores and mesostructured skeletons prepared by combining the alkoxy-derived sol–gel process accompanied by phase separation and the solvothermal process. Chem Mater 20:2165–2173

    Article  Google Scholar 

  11. 11.

    Tokudome Y, Fujita K, Nakanishi K, Miura K, Hirao K (2007) Synthesis of monolithic Al2O3 with well-defined macropores and mesostructured skeletons via the sol–gel process accompanied by phase separation. Chem Mater 19:3393–3398

    Article  Google Scholar 

  12. 12.

    Schubert U, Hüsing N (2012) Synthesis of inorganic materials. CPI Group Ltd, Croydon, UK, Chapter 4

    Google Scholar 

  13. 13.

    Gash AE, Tillotson TM, Satcher Jr JH, Poco JF, Hrubesh LW, Simpson RL (2001) Use of epoxides in the sol-gel synthesis of porous iron (III) oxide monoliths from Fe (III) salts. Chem Mater 13:999–1007

    Article  Google Scholar 

  14. 14.

    Baumann TF, Gash AE, Chinn SC, Sawvel AM, Maxwell RS, Satcher JH (2005) Synthesis of high-surface-area alumina aerogels without the use of alkoxide precursors. Chem Mater 17:395–401

    Article  Google Scholar 

  15. 15.

    Kido Y, Nakanishi K, Miyasaka A, Kanamori K (2012) Synthesis of monolithic hierarchically porous iron-based xerogels from iron (III) salts via an epoxide-mediated sol-gel process. Chem Mater 24:2071–2077

    Article  Google Scholar 

  16. 16.

    Kido Y, Nakanishi K, Okumura N, Kanamori K (2013) Hierarchically porous nickel/carbon composite monoliths prepared by sol-gel method from an ionic precursor. Microporous Mesoporous Mater 176:64–70

    Article  Google Scholar 

  17. 17.

    Kido Y, Hasegawa G, Kanamori K, Nakanishi K (2014) Porous chromium-based ceramic monoliths: oxides (Cr2O3), nitrides (CrN), and carbides (Cr3C2). J Mater Chem A 2:745–752

    Article  Google Scholar 

  18. 18.

    Fukumoto S, Nakanishi K, Kanamori K (2015) Direct preparation and conversion of copper hydroxide-based monolithic xerogels with hierarchical pores. New J Chem 39:6771–6777

    Article  Google Scholar 

  19. 19.

    Gash AE, Satcher Jr JH, Simpson RL (2004) J Non-Cryst Solids 350:145–151

    Article  Google Scholar 

  20. 20.

    Liu M, Yan X, Liu H, Yu W (2000) An investigation of the interaction between polyvinylpyrrolidone and metal cations. React Funct Polym 44:55–64

    Article  Google Scholar 

Download references

Acknowledgements

The present study has been performed under financial supports from Advanced Low Carbon Technology Research and Development Program (ALCA, Japan Science and Technology Agency).

Author information

Affiliations

Authors

Corresponding author

Correspondence to Kazuki Nakanishi.

Ethics declarations

Conflict of interest

The authors declare that they have no conflict of interest.

Additional information

Highlights

  • Hierarchically porous magnesium oxide (divalent metal oxide) monoliths with three-dimension network structure are synthesized.

  • The network structure can be preserved after heat treatment under oxidative conditions.

  • The fraction of pores larger than 30 nm can be controlled by addition of 1,3,5-benzenetricarboxylic acid.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Lu, X., Kanamori, K. & Nakanishi, K. Synthesis of hierarchically porous MgO monoliths with continuous structure via sol–gel process accompanied by phase separation. J Sol-Gel Sci Technol 89, 29–36 (2019). https://doi.org/10.1007/s10971-018-4682-2

Download citation

Keywords

  • Magnesium oxide
  • Sol–gel
  • Phase separation
  • Hierarchical pore structure
  • Monoliths