Hybrid porous materials with high surface area derived from bromophenylethenyl-functionalized cubic siloxane-based building units

Sonogashira cross-coupling of bromophenylethenyl-terminated cubic, double four-ring, siloxane cages with di-/triethynyl compounds results in microporous poly(ethynylene aryleneethenylene silsesquioxane) networks, simply termed as polyorganosiloxane networks (PSNs). In comparison with porous organic polymers reported previously, these PSNs show relatively high surface area and comparable thermal stability. Their apparent BET specific surface areas vary in the range of 850-1040 m²g^-1 depending on the length and the connectable sites of the ethynyl compounds. Analyses of pore size distribution revealed bimodal micropores with relatively narrow distribution. The degree of cross-linking affects the degree of cleavage of the siloxane bonds, and this suggests that partial cleavage of the siloxane cages is mainly a result of cage distortion. Hydrogen adsorption was performed to evaluate potential of the PSNs as hydrogen storage media. Uptakes of up to 1.19 wt % at 77 K and 760 Torr and initial isosteric heats of adsorption as high as 8.0 kJ mol^-1 were observed. These materials have been obtained by a combination of structural, synthetic organic, and materials chemistry, which can exploited to synthesize porous hybrid materials with specifically designed structures and functions.