The molecular catalyst CotpyP (0.025 mL 50 nmol, 2 mM in H2O) and 0.025 mL H2O (to reach was then degassed for one min (vacuum at 10 -2 mbar) after which 13 CO2 (1 bar) was introduced. The photoreactor (kept at 25 °C and stirred at 600 rpm) was then irradiated (AM 1.5G, 100 mW cm -2 ). The headspace was then transferred to an air-tight evacuated IR cell (10 cm path length, equipped with KBr windows) and the background (IR cell under vacuum)