Hypercrosslinked polymers (HCPs) synthesized by copolymerisation of p-dichloroxylene (p-DCX) and 4,4′-bis(chloromethyl)-1,1′-biphenyl (BCMBP) constitute a family of low density porous materials with excellent textural development. Such polymers show microporosity and mesoporosity and exhibit Brunauer–Emmett–Teller (BET) surface areas of up to 1970 m2 g−1. The CO2 adsorption capacity of these polymers was evaluated using a thermogravimetric analyser (atmospheric pressure tests) and a high-pressure magnetic suspension balance (high pressure tests). CO2 capture capacities were related to the textural properties of the HCPs. The performance of these materials to adsorb CO2 at atmospheric pressure was characterized by maximum CO2 uptakes of 1.7 mmol g−1 (7.4 wt%) at 298 K. At higher pressures (30 bar), the polymers show CO2 uptakes of up to 13.4 mmol g−1 (59 wt%), superior to zeolite-based materials (zeolite 13X, zeolite NaX) and commercial activated carbons (BPL, Norit R). In addition, these polymers showed low isosteric heats of CO2 adsorption and good selectivity towards CO2. Hypercrosslinked polymers have potential to be applied as CO2 adsorbents in pre-combustion capture processes where high CO2 partial pressures are involved.