Fundamental Insights into Photoelectrocatalytic Hydrogen Production with a Hole-Transport Bismuth Metal–Organic Framework

Solar fuels production is a cornerstone in the development
of emerging
sustainable energy conversion and storage technologies. Light-induced
H2 production from water represents one of the most crucial
challenges to produce renewable fuel. Metal–organic frameworks
(MOFs) are being investigated in this process, due to the ability
to assemble new structures with the use of suitable photoactive building
blocks. However, the identification of the reaction intermediates
remains elusive, having negative impacts in the design of more efficient
materials. Here, we report the synthesis and characterization of a
new MOF prepared with the use of bismuth and dithieno­[3,2-b:2′,3′-d]­thiophene-2,6-dicarboxylic
acid (DTTDC), an electron-rich linker with hole transport ability.
By combining theoretical studies and time-resolved spectroscopies,
such as core hole clock and laser flash photolysis measurements, we
have completed a comprehensive study at different time scales (fs
to ms) to determine the effect of competitive reactions on the overall
H2 production. We detect the formation of an intermediate
radical anion upon reaction of photogenerated holes with an electron
donor, which plays a key role in the photoelectrocatalytic processes.
These results shed new light on the use of MOFs for solar fuel production.