We fabricated three crosslinked porphyrin-based polyimides (PPBPI-CRs) from PEPHQDA, TAPP and three terminal anhydrides (PA, PEPA and PENA) via alkynyl groups crosslinking reactions. PPBPI-CRs had permanent porosities and revealed outstanding thermal stabilities. Affected by π-stacking and molecular sizes effect, with increasing conjugate and molecular sizes effect in different terminal anhydrides, porphyrin-based polyimides (PPBPIs) revealed decreased specific surface areas (106.8 – 8.3 m2 g-1), whereas, PPBPI-CRs showed increased BET surface areas (1.8 - 633 m2 g-1). Meanwhile, PPBPI-CRs had considerable CO2 uptakes (1.37, 2.01 and 2.37 mmol g-1) and isosteric heats of CO2 adsorption (34.8, 27.5 and 22.6 kJ/mol). The PPBPI-CRs had CO2/N2 (39.83, 36.95, 40.08) and CO2/CH4 (14.13, 9.78, 10.87) separation selectivities.