Microporous Cyanate Resins:
Synthesis, Porous Structure, and Correlations with Gas and Vapor Adsorptions
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Abstract
Three silicon and nitrogen-centered cyanate monomers
tetrakis(4-cyanatophenyl)silane, tetrakis(4-cyanatobiphenyl)silane,
and tris(4-cyanatobiphenyl)amine were designed and synthesized, which
were then polymerized via thermal cyclotrimerization reaction to create
highly porous cyanate resin networks with systematically varied nodes
and linking struts. The chemical structures of monomers and polymers
were confirmed by <sup>1</sup>H NMR, FTIR, solid-state <sup>13</sup>C CP/MAS NMR spectra, and elemental analysis. The products are amorphous
with 5% weight-loss temperatures over 428 °C. The results based
on N<sub>2</sub> and CO<sub>2</sub> adsorption isotherms show that
the pores in these polymers mainly locate in the microporous region,
and the BET surface areas are up to 960 m<sup>2</sup> g<sup>–1</sup>, which is the highest value for the porous cyanate resin reported
to date. The nitrogen- and oxygen-rich characteristics of cyanate
resins lead to the networks strong affinity for CO<sub>2</sub> and
thereby high CO<sub>2</sub> adsorption capacity of 11.1 wt % at 273
K and 1.0 bar. The adsorption behaviors of H<sub>2</sub>, CO<sub>2</sub>, benzene, <i>n</i>-hexane, and water vapors were investigated
by correlating with the chemical composition and porosity parameters
of the networks as well as the physicochemical nature of adsorbates
