Molecular Z-Scheme for Solar Fuel Production via Dual Photocatalytic Cycles

Natural photosynthesis uses an array of molecular structures in a multi-photon Z-scheme for the conversion of light energy into chemical bonds (i.e., solar fuels). Here we show that upon excitation of both a molecular photocatalyst (PC) and a substituted naphthol (ROH) in the presence of a sacrificial electron donor and proton source, we achieve artificial photosynthesis of H2. Data support a multi-photon mechanism that is catalytic with respect to both PC and ROH. The use of a naphthol molecule as both a light absorber and H2 producing catalyst is a unique motif for Z-scheme systems. This molecular Z-scheme can drive a reaction that is uphill by 511 kJ/mol and circumvents the high energy constraints associated with reduction of weak acids in their ground-state, thus offering a new paradigm for the production of solar fuels.