Porous coordination polymers (PCPs), constructed from organic linkers and metal ions, can provide special pore environments for selective CO₂ capture. Although many PCPs have been reported, a rational design for identifying PCPs that adsorb CO₂ molecules with a low binding energy, high separation ability and high chemical stability remains a great challenge. Here, we propose and validate, experimentally and computationally, a new PCP, [La(BTN)DMF]·guest (PCP-1⊃guest), that has a large aromatic organic surface and a low binding energy for high CO₂ separation from four-gas mixtures (CO₂–N₂–O₂–CO) at ambient temperature. In addition, it shows good water and chemical stability; in particular, it is stable from pH = 2 to 12 at 100 °C, which is unprecedented for carboxylate-based PCPs.