Soluble Supertetrahedral Chalcogenido T4 Clusters: High Stability and Enhanced Hydrogen Evolution Activities.

The discrete supertetrahedral chalcogenido T n clusters can be regarded as a type of quantum dot (QD) with precise structure and uniform size. They were commonly studied in the solid state because of their poor solubility or highly negative charge that leads to instability in common solvents. These drawbacks limit their potential applications as efficient photocatalysts. Herein we first obtained a sulfide compound via an ionic-liquid-assisted precursor method, namely, (BMMim)(CdInSCl) (T4-1, BMMim = 1-butyl-2,3-dimethylimidazolium). T4-1 is characteristic of the discrete anionic T4 cluster and is insoluble in common solvents. Introducing Se into the structure resulted in compounds (BMMim)(CdInSSeCl) (T4-2) and (BMMim)(CdInSeCl)(4,4'-bpy) (T4-3) with narrower band gaps. Moreover, T4-2 and T4-3 were soluble in dimethyl sulfoxide (DMSO) probably because of weaker interactions between cations and anions than in T4-1. The solution stability of these clusters has been confirmed by mass spectrometry. Further characterization reveals that the highly dispersed T4 clusters exposed more active sites in solution, so their rates of relevant H production were improved to be ∼5 times that in the solid state. To our knowledge, this is the first time that highly dispersed T n clusters have been applied in photocatalytic H generation.