Monomer building units play a key role in the porosity and adsorption performance of porous conjugated polymers. Three tetracarbazolyl-substituted monomers (Cz-810) with similar molecular structures were designed and prepared in order to tune the porosity and pore size distribution of the obtained porous conjugated polycarbazoles (CPOP-810) via FeCl3-promoted carbazole-based oxidative coupling polymerization. Polymers CPOP-8 and CPOP-10 exhibit microporous nature similar to most of reported conjugated microporous polymers. Porosity analysis and adsorption performance indicate that CPOP-9 is predominantly mesoporous. The BrunauerEmmettTeller specific surface area of CPOP-9 is up to 2440 m(2) g(1), which is the highest specific surface area among the reported porous conjugated polycarbazoles by the same method. Mesoporous CPOP-9 shows higher water vapor uptake capacity (804 mg g(1)) than microporous polymers CPOP-8 (208 mg g(1)) and CPOP-10 (181 mg g(1)) at water saturated vapor pressure and 298 K, which might imply that pore size has a key effect on wettability of the porous polymers. With high specific surface area and pore volume, CPOP-9 exhibits high hydrogen uptake of 5.22 wt % (77 K) and carbon dioxide uptake of 70.0 wt % (298 K) at 18.0 bar. Additionally, the uptake capacity of CPOP-9 for toluene is high up to 1355 mg g(1) at the saturated vapor pressure (298 K). The adsorption performance of CPOP-9 can be comparable with that of the known porous organic polymers with ultrahigh specific surface area, such as PAF-1 and PNN-4, under the same conditions.