Molecular solid solution of lanthanide-titanium-oxo clusters with enhanced photocatalytic hydrogen evolution

Molecular solid solutions of metal clusters containing different metal centers with well-defined structures can accurately regulate the HOMO-LUMO gap, but are rarely available. Herein, a series of colorless lanthanide-titanium-oxo clusters Ln 2 Ti 4 ( μ 2 -O) 2 ( μ 3 -O) 4 (Piv) 10 (THF) 2 (Ln 2 Ti 4 , Ln = Eu, Gd, Tb, and Ce, HPiv = pivalic acid) were synthesized by the reaction of pivalic acid with Ln(Ac) 3 and titanium isopropoxide. The light yellow crystal of cluster solid solutions Eu 2 Ti 4− x Cd x , containing a mixture of Eu 2 Ti 4 and Eu 2 Ti 3 Cd, was obtained by in situ doping Cd 2+ and S 2− . Eu 2 Ti 3.92 Cd 0.08 displays efficient photocatalytic hydrogen evolution activity without a co-catalyst, which is up to 2.6 times that of Eu 2 Ti 4 . Femtosecond time-resolved transient absorption spectroscopy and spin-polarized density functional calculations showed that the enhanced photocatalytic performance of Eu 2 Ti 4− x Cd x can be attributed to the narrower HOMO-LUMO gap and lower LUMO position than that of Eu 2 Ti 4 . This studyprovides an in situ doping method to realize the simple preparation of cluster solid solution.