A consolidated ionothermal strategy was developed for the polymerization of thermally unstable nitriles to construct high performance materials with permanent porosity, and carbazole, dibenzofuran, and dibenzothiophene were separately introduced into covalent triazine-based networks to investigate the effects of heterocycles on the gas adsorption performance. Three nitriles, namely 3,6-dicyano-carbazole, 3,6-dicyanodibenzofuran, and 3,6-dicyanodibenzothiophene, were designed and synthesized, which were readily converted to heat-resistant intermediates at a moderate temperature and then polymerized to create highly porous poly(triazine) networks instead of the traditional one-step procedure. This documents an improved strategy for the successful construction of heterocyclic-functional triazine-based materials. The chemical structures of monomers and polymers were confirmed by H-1 NMR, FTIR, and elemental analysis. Such polymers with high physical chemical stability and comparable BET surface areas can uptake 1.44 wt % H-2 at 77 K/1 bar and 14.0 wt % CO2 at 273 K/1 bar and present a high selectivity for gas adsorption of CO2 (CO2/N-2 ideal selectivity up to 45 at 273K/1.0 bar). The nitrogen- and oxygen-rich characteristics of carbazole and dibenzofuran feature the networks strong affinity for CO2 and thereby high CO2 adsorption capacity. This also helps to thoroughly understand the influence of pore structure and chemical composition on the adsorption properties of small gas molecules.