The photochemical working scheme is depicted in Figure . In the bicarbonate buffer, the ground state photoacid (pyranine, λabs,max = 400 nm) is excited upon irradiation with blue light (427 nm). The excited state of the photoacid, with a pKa* value of 0.6, undergoes deprotonation within the pH range of 6 to 8 of the solution. Consequently, the released proton reduces the pH of the local environment, causing the bicarbonate ions to decompose into CO2 and H2O. Upon return to a dark environment, the photoswitch transitions back to the ground state, acquiring a proton from the bicarbonate ions and generating carbonate ions. These carbonate ions actively participate in capturing CO2 from the dilute source. Through this lightdark cycle, CO2 can be separated and concentrated.