The photocatalytic reactions with the self-assembled TiO2|CotpyP (10 or 5 nmol mgTiO2 -1 CotpyP) were carried out in a mixture of 2:1 MeCN:carbonate buffer (with the carbonate buffer containing the PET monomers). The presence of MeCN shifts the conduction band of TiO2 to a more negative potential, facilitating the turnover of the molecular cobalt catalyst. Only a low yield of CO (21±5 µmol gsub -1 ; 1.8±0.4 µmol gcat -1 h -1 after 48 h; Figure ) was observed (with 10 nmol mgTiO2 -1 CotpyP) in the presence of both EG and TPA (obtained after LCC-pre-treatment of PET film) in the medium, suggesting the inhibitory effect of TPA by interfering with the Co-based catalysis (the yields and activity of the accompanied H2 evolution reaction are provided in Table ). Therefore, the reactions were next performed after precipitating TPA from the pre-treated solution (by acidification), followed by neutralization (back to pH ~6.5; clear solution with no residues) to make the pH conducive for the CO2 reduction reaction (Figure , see Experimental Section for details). After TPA removal, the yield (80±6 µmol gsub -1 ) and activity (7±0.5 µmol gcat -1 h -1 ; TONCO=32) for CO production improved significantly after 48 h with 10 nmol mgTiO2 -1 CotpyP (Figure ). Additionally, on using a lower (5 nmol mgTiO2 -1 ) CotpyP concentration, the TONCO further increased to 56, with no compromise in CO production (with a CO selectivity of ~20%) and H2 as the major reduction product (Figure ; Table ). Control experiments in the absence of photocatalyst or light did not result in product formation (Table ). Interestingly, in the absence of externally-purged CO2, CO production was still observed, although ~40-50% less as compared to CO2-purging (Table ). Time-dependent evolution plots (using EG and no external CO2 purging) in Figure reveal the evolution of CO2, but negligible CO production at initial stages. However, after 24 h, the amount of CO increased and exceeded that of the CO2 generated in-situ. These observations suggest that the TiO2|CotpyP photocatalyst may also reduce the CO2 generated in-situ from the overoxidation of EG under the given conditions. Additionally, a non-quantifiable small fraction of CO may also form from partial oxidation/decarbonylation of EG, contributing to the total CO yield.