A Semiconducting Bi₂O₂(C₄O₄) Coordination Polymer Showing a Photoelectric Response

Inorganic semiconductors are extensively considered to be among the most promising materials to convert solar light into electricity or chemical energy owing to their efficiency in the separation of photoinduced electron/hole. Bismuth oxides, and, in particular, those built up of [Bi₂O₂]²⁺ layers, show an efficient charge separation and, thus, high photocatalytic activities. To explore a possible synergetic effect of bismuth metallic nodes combined with the electron-rich linker squarate, Bi₂O₂(C₄O₄) or IEF-3 (an IMDEA Energy framework) was hydrothermally prepared and adequately characterized. As determined from the X-ray structure, [Bi₂O₂]²⁺ layers are interconnected by squarate ligands, having a pronounced effect of the 6s² lone pair on the bismuth local environment. IEF-3 shows high thermal and chemical robustness at industrially relevant model aggressive media. A large panel of physicochemical methods were applied to recognize IEF-3 as an UV-absorbing n-type semiconductor, showing a photocurrent response comparable to that of α-Bi₂O₃, offering further possibilities for tuning its electrochemical properties by modifying the ligand. In this way, the well-known compositional and structural versatility of coordination polymers may be applied in the future to fine-tune metal-organic semiconductor systems.