To a glass photoreactor vial (7.7 mL total volume) equipped with a magnetic stir bar was added 5 mg of TiO2 suspended in 1 mL of an aqueous stock solution (containing 60 mM EG, 60 mM TPA, 117 mM NaH 13 CO3 and 100 mM NaCl, pH 6.5) followed by 2 ml of MeCN. The molecular catalyst CotpyP (0.025 mL 50 nmol, 2 mM in H2O) was added and the photoreactor was capped with a rubber septum. The photoreactor was then degassed for 1 min (vacuum at 10 -2 mbar) after which 12 CO2 or 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 ) for 48 h. The headspace was transferred to an air-tight evacuated IR cell (10 cm path length, equipped with KBr windows) and the background (IR cell under vacuum) corrected IR spectrum was recorded to detect CO and 13 CO. Isotopic labelling experiments were also performed with the stock solution followed by the TPA precipitation protocol before and after neutralization with 1 M NaOH (see Photoreforming of enzyme pre-treated PET for CO2 reduction).