N-containing porous organic polymers and derived porous carbons are promising for CO2 capture, while their simple fabrication still remains a challenge. Herein, the porphyrin-based triazine polymers were simply constructed from tetraphenylporphyrin and cyanuric chloride according to one-pot Scholl coupling reaction and Friedel-Crafts reaction. The as-fabricated polymers had the maximum CO2 uptake of 173 mg/g and high CO2/N-2 selectivity (IAST: 59.35) at 273 K and 1.0 bar. After KOH-activated carbonization, the Brunauer-Emmett-Teller surface area (1004-3238 m(2)/g), micropore area (798-1434 m(2)/g), pore volume (0.54-1.76 cm(3)/g), micropore volume (0.41-1.02 cm(3)/g), and ultra-micropore volume (up to 0.29 cm(3)/g) were significantly improved, indicative of their outstanding CO2 uptakes (171-282 mg/g). The ultramicropore volume with a pore size of less than 1.2 nm and N content were proven to be the vital factors for CO2 capture. The synthetic strategy provides a simple and effective approach for the synthesis of the porphyrin-based triazine polymers, and the derived porous carbons were efficient for CO2 capture.