It remains a great challenge to design and synthesize a porous material for CO₂ capture and sensing simultaneously. Herein, strategy of “cage to frameworks” is demonstrated to synthesize fluorescent porous organic polymer (pTOC) by using tetraphenylethylene‐based oxacalixarene cage (TOC) as the monomer. The networked cages (pTOC) have improved porous properties, including Brunauer–Emmett–Teller surface area and CO₂ capture compared with its monomer TOC, because the polymerization overcomes the window‐to‐arene packing modes of cages and turns on their pores. Moreover, pTOC displays prominent reversible fluorescence enhancement in the presence of CO₂ in different dispersion systems and fluorescence recovery for CO₂ release in the presence of NH₃·H₂O, and is thus very effective to detect and quantify the fractions of CO₂ in a gaseous mixtures.