Three silicon and nitrogen-centered cyanate monomers tetrakis(4-cyanatophenyl)silane, tetrakis(4-cyanato-biphenyl)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 H-1 NMR, FTIR, solid-state C-13 CP/MAS NMR spectra, and elemental analysis. The products are amorphous with 5% weight-loss temperatures over 428 degrees C. The results based on N-2 and CO2 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(2) g(-1), 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 CO2 and thereby high CO2 adsorption capacity of 11.1 wt % at 273 K and 1.0 bar. The adsorption behaviors of H-2, CO2, benzene, n-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.