Microporosity and CO2 Capture Properties of Amorphous Silicon Oxynitride Derived from Novel Polyalkoxysilsesquiazanes

作者：Iwase Yoshiaki; Horie Yoji; Honda Sawao; Daiko Yusuke; Iwamoto Yuji^*

来源：Materials, 2018, 11(3): 422.

DOI：10.3390/ma11030422

• silicon oxynitride
• amorphous state
• microporosity
• CO2 adsorption capacity
• polymer-derived ceramics (PDCs)

Polyalkoxysilsesquiazanes ([ROSi(NH)(1.5)](n), ROSZ, R = Et, nPr, iPr, nBu, sBu, nHex, sHex, cHex, decahydronaphthyl (DHNp)) were synthesized by ammonolysis at -78 degrees C of alkoxytrichlorosilane (ROSiCl3), which was isolated by distillation as a reaction product of SiCl4 and ROH. The simultaneous thermogravimetric and mass spectrometry analyses of the ROSZs under helium revealed a common decomposition reaction, the cleavage of the oxygen-carbon bond of the RO group to evolve alkene as a main gaseous species formed in-situ, leading to the formation of microporous amorphous Si-O-N at 550 degrees C to 800 degrees C. The microporosity in terms of the peak of the pore size distribution curve located within the micropore size range (<2 nm) and the total micropore volume, as well as the specific surface area (SSA) of the Si-O-N, increased consistently with the molecular size estimated for the alkene formed in-situ during the pyrolysis. The CO2 capture capacity at 0 degrees C of the Si-O-N material increased consistently with its SSA, and an excellent CO2 capture capacity of 3.9 mmol.g(-1) at 0 degrees C and CO2 1 atm was achieved for the Si-O-N derived from DHNpOSZ having an SSA of 750 m(2).g(-1). The CO2 capture properties were further discussed based on their temperature dependency, and a surface functional group of the Si-O-N formed in-situ during the polymer/ceramics thermal conversion.

• 出版日期2018-3