Cooperative Crystallization of Chiral Heterometallic Indium(III)–Potassium(I) Metal–Organic Frameworks as Photosensitizers in Luminescence Sensors and Dye-Sensitized Solar Cells

In this work, the coexistence of In­(III) and K­(I) induces a rapid crystal growth of single crystals of heterometallic metal–organic frameworks (MOFs), [In_0.5K­(3-qlc)­Cl_1.5(H₂O)_0.5]_2<i>n</i> (<b>1</b>) and [InK­(ox)₂­(H₂O)₄]_<i>n</i> (<b>2</b>) (3-Hqlc = quinoline-3-carboxylic acid; H₂ox = oxalic acid). Remarkably, with the help of achiral 3-Hqlc, compound <b>1</b> represents the chiral interpenetrating p-block heterometallic MOFs with helical chain along the 4₃ screw axis, while compound <b>2</b> possesses a highly symmetric (4,4,4)-connected topology network with a Schläfli symbol of (4²·8³·10)­(4²·8⁴). Consideration of two different organic ligands viz. 3-Hqlc and H₂ox constructed heterometallic MOFs with different geometrical dimensions of unit cells, their influences on luminescence and photovoltaic properties are studied. Compounds <b>1</b> and <b>2</b> show tunable luminescence from blue to yellow and white by varying the temperature in the solid state. Encouraged by the UV–visible absorption and HOMO–LUMO energy states matched for sensitizing TiO₂, the two compounds are employed in combination with N719 in dye-sensitized solar cells (DSSCs) to compensate for absorption in the region of ultraviolet and blue-violet. Under optimized conditions, the DSSCs devices using cosensitizers of <b>1</b>/N719 and <b>2</b>/N719 display an overall conversion efficiency of 8.07% and 7.42%, which is 22.09% and 12.25% higher than that of a device solely sensitized by N719 (6.61%). Consequently, both of the two compounds could serve as excellent photosensitizers and application in luminescence sensors and DSSCs