Titanium oxides and bismuth halides or oxyhalides have been known to be excellent semiconductors with both excellent photocatalytic and photoelectric properties. The design of supersalts assembled by titanium-oxo clusters (TOCs) and bismuth iodide clusters is a hopeful strategy for exploring the chemistry and application of new titanium-oxo clusters. We report herein a series of unusual ionic TOCs with Ti12 oxo cluster cations and bismuth iodide anions, [Ti12O15(OiPr)17]3[Bi3I12] (Bi3), [Ti12O14(OiPr)18][Bi4I14(THF)2] (Bi4), and [Ti12O14(OiPr)18][Ti11BiO14(OiPr)17][Bi6I22] (Bi6). Single-crystal X-ray analysis revealed that the type and charge of the Ti12 clusters varied with the charges of different bismuth iodide clusters. Taking advantage of the easy hydrolysis of the TOCs and BiI clusters in water, we used these supersalt crystals as single-source precursors to prepare a p-n-type BiOI-TiO photocatalyst. The heterojunction materials were carefully characterized by powder X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, etc. The synergistic effect of the two components of BiOI and TiO on the photocatalytic degradation of RhB in water is demonstrated. This is a very convenient method for obtaining a p-n-type BiOI-TiO heterojuction photocatalyst by just placing the ground TOC crystals into water.