Continuous CO ₂ Capture with Photochemical Release in a Slug Flow Reactor

CO 2 capture and release via a light-driven pH swing offers a promising route to carbon management by harnessing sunlight and reducing reliance on external energy inputs. Recent studies have explored diverse photoactive compounds, yet the engineering of light-driven CO 2 separation systems remains underexplored. We introduce a microfluidic slug flow reactor that couples efficient light delivery with molecular p K a alignment to drive separation. A synthesized polymeric photoacid with a high ground-state p K a (∼10) remains protonated in the dark during CO 2 absorption and deprotonates under illumination to drive CO 2 release. Since higher loadings attenuate light and confine activation near the surface, we tuned illumination depth and reactor geometry to maintain uniform activation and sustained operation, with stable performance over 125 h, releasing 34 mmol of CO 2 captured from a 5% CO 2 /3% O 2 feed while minimizing photothermal effects. Overall, this architecture provides a versatile platform for coupling with future advanced photoactive chemistries.