Enhancing CO₂ to Alcohol Conversion: Powerful Photocatalysts Based on TiO₂-Cu(I)-Iodine-Pyridine One-Dimensional...

Coordination polymers (CPs) are promising materials for environmental applications, particularly in catalysis, due to their flexible structures, tunable electronic properties, and adaptable surface chemistry. This study reports the one-step, room-temperature synthesis of five 1D Cu(I)-iodide-pyridine based CPs with the general formula [CuI(L)]_n, where L represents different pyridine derivatives: pyridine (CP1), 3-methylpyridine (CP2), 4-methylpyridine (CP3), 2-amino-4-methylpyridine (CP4), and 2-chloro-4-methylpyridine (CP5). All of the compounds exhibit band gap energies around 3 eV, making them suitable candidates for photocatalytic applications. Indeed, the study investigates the photoreduction of CO₂ to alcohols using a heterogeneous photocatalytic system consisting of TiO₂ and varying proportions of CPs. The reactor design enables the rapid removal of produced alcohols, preventing them from being oxidized by TiO₂ as sacrificial materials and thus achieving near-zero net alcohol production. The optimal TiO₂@CP mixture, TiO₂@5%CP4, demonstrated higher chemical stability due to the amine substituent on the pyridine, which facilitates hydrogen bonding between CP chains, and an enhanced ability to interact with CO₂, as confirmed by adsorption experiments and DFT calculations. The optimized mixture achieved selective methanol production of 894 μg·g cat ^-1·h ^-1, significantly surpassing the benchmark photocatalytic system TiO₂@3%CuO (318 μg·g cat ^-1·h ^-1). Furthermore, TiO₂@5%CP4 maintained stable photocatalytic performance over 10 h without noticeable degradation.