We report a facile method for the preparation of hypercrosslinked carbazole-based porous organic polymers (CPOPs) via FeCl3-promoted one-step oxidative coupling reaction and Friedel–Crafts alkylation in one pot. The Brunauer–Emmett–Teller specific surface area of the obtained polymers is up to 1190 m2 g−1, which is competitive with the reported results for other hypercrosslinked porous polymers. Gas (hydrogen and carbon dioxide) adsorption isotherms show that their hydrogen storage is up to 1.29 wt% at 1.0 bar and 77 K, and the uptake capacity for carbon dioxide can reach 16.8 wt% at 1.0 bar and 273 K, which makes them promising candidates for applications in the energy and environment fields. Furthermore, the amount of toluene adsorbed by CPOP-15 is high, around 1470 mg g−1 (about 16.0 mmol g−1) at the saturated vapor pressure and the mass ratio of adsorbed water to toluene is up to 1:7. Moreover, the prepared CPOPs possess excellent adsorption capacities for formaldehyde (10.7 mg g−1) at ambient conditions and exhibit good thermal stability and reusability, at the same time, which makes them show potential in applications to eliminate harmful small molecules from the environment.