Photoaccumulation of Long-Lived Reactive Electrons in a Microporous Ti(IV) Oxocluster-Based Metal-Organic Framework...

The microporous Ti₁₂ oxocluster-based metal-organic framework (MOF) MIP-177(Ti)-LT exhibits excellent stability and photoactivity, making it highly promising for photocatalysis. Using transient and photoinduced absorption spectroscopies, the behavior of reactive electrons in MIP-177(Ti)-LT across femtosecond-to-second timescales is investigated. The framework shows efficient charge separation and slow decay kinetics, with photogenerated charges persisting into the microsecond-second (µs-s) range and displaying higher yields and slower recombination than benchmark MOFs MIL-125(Ti)-NH₂ and UiO-66(Zr)-NH₂. Photogenerated holes oxidize water with an O₂ yield of 335 µmol g^-1 h^-1 in the presence of electron scavengers. Under continuous irradiation, long-lived electrons accumulate, further enhanced by a hole scavenger (methanol). Remarkably, these electrons persist over 48 h post-excitation under argon, accompanied by a reversible white-to-black color change. The stored electrons remain redox-active, efficiently reducing added O₂ and methyl viologen. Dark addition of a Pt co-catalyst to photocharged MIP-177(Ti)-LT induces H₂ evolution at ≈300 µmol g^-1 (≈58 C g^-1), corresponding to an accumulated electron density of one electron per 12 Ti atoms. These results highlight the photocharging properties of MIP-177(Ti)-LT and its potential for sustainable photocatalytic applications.