Enhancing CO ₂ to Alcohol Conversion: Powerful Photocatalysts Based on TiO ₂ –Cu(I)-Iodine-Pyridine One-Dimensional Coordination Polymers

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)]_<i>n</i>, where L represents different pyridine derivatives: pyridine (<b>CP1</b>), 3-methylpyridine (<b>CP2</b>), 4-methylpyridine (<b>CP3</b>), 2-amino-4-methylpyridine (<b>CP4</b>), and 2-chloro-4-methylpyridine (<b>CP5</b>). 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 <b>TiO</b><b>₂</b><b>@CP</b> mixture, <b>TiO</b><b>₂</b><b>@5%CP4</b>, 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 <b>TiO</b><b>₂</b><b>@3%CuO</b> (318 μg·g cat ^-1·h ^-1). Furthermore, <b>TiO</b><b>₂</b><b>@5%CP4</b> maintained stable photocatalytic performance over 10 h without noticeable degradation.