Emergent integration of the amine scrubbing method into photocatalytic CO₂ reduction

Developing strategies for photocatalytic reduction of low-concentration CO₂ under ambient conditions is essential for mitigating global warming and addressing energy and carbon resource shortages. The amine scrubbing method (ASM), which captures dilute CO₂ as carbamic acid using low-cost primary and secondary amines, is widely employed to generate concentrated CO₂. However, releasing CO₂ from carbamic acid to generate highly concentrated CO₂ requires high-temperature heating, resulting in substantial energy consumption and cost. Herein, we report the integration of ASM with photocatalytic CO₂ reduction. A newly synthesized complex [Ru(bpy)(P-P)(CO)(H)]⁺ (Ru-H⁺; bpy = 2,2'-bipyridine, P-P = Ph₂PC₂H₄PPh₂) serves as an efficient catalyst for reducing CO₂ at low concentrations, even below 0.34%, in the presence of an Ir-based photosensitizer and a reductant (TON_HCOOH ≥ 1925, Φ _HCOOH = 39%, selectivity_HCOOH > 97%). This system quantitatively converts CO₂ captured by amines such as monoethanolamine into formic acid at room temperature. In this process, CO₂ released from carbamic acid in solution is rapidly consumed via photocatalytic reduction, enabling efficient utilization of low-concentration CO₂ without requiring energy-intensive regeneration processes.