Hypercrosslinked Siloxane–Organic Hybrid with Hierarchical Pores and Ultrahigh Surface Area Via Self-Condensation of Functionalized Cubic Siloxane Cages

Designed synthesis of a priori nanoporous materials with tunable structures and properties is a scientific and technological challenge in chemistry and engineering. A bottom-up self-assembly of well-defined molecular building blocks has settled at the center of synthetic chemistry as a strategic route to construct novel nanoporous architectures. The double four-ring (D4R) siloxane cage, also known as cubic polyhedral silsesquioxane (POSS), and its organic derivatives have been utilized as building units to produce porous materials; however, control over molecular homogeneity of the obtained porous materials is still a great challenge. Recently, we succeeded in syntheses of novel microporous hybrids possessing narrow pore size distribution and high surface area via covalent-linking of the D4R cages and rigid aromatic linkers [1,2]. In this presentation, we have focused on the increase in surface area of the siloxane–organic hybrid through the increase in the degree of cross-linking. Specifically, a novel hierarchically-porous siloxane–organic hybrid has been synthesized by the Friedel–Crafts self-condensation of benzyl chloride-terminated D4R siloxane cages as a singular molecular precursor. The resulting material exhibits ultrahigh surface area (BET surface area of 2330 m² g⁻¹), large pore volume, and high H₂ uptake capacity.

References

[1] W. Chaikittisilp, A. Sugawara, A. Shimojima, T. Okubo, Chem. Eur. J. 2010, 16, 6006-6014.

[2] W. Chaikittisilp, A. Sugawara, A. Shimojima, T. Okubo, Chem. Mater. 2010, 22, 4841-4843.