A novel strategy to improve gas capture performance of metal-free azo-bridged porphyrin porous organic polymers: The design of traps

•We synthesized two metal-free azo-bridged porphyrin porous organic polymers with a linear and bent backbone, respectively.•In comparison with the linear backbone, the bent backbone results in a lower extent of reaction, poorer network structure, smaller SBET value and special trap structure.•The traps in PDAPP are beneficial to the adsorption of larger sized gas molecules like CO2 and CH4.•CO2 and CH4 molecules are easy to enter the traps, but hard to get out of them.•POPs with traps are potential high-efficiency gas uptake materials.