Semiartificial Photosynthetic\nNanoreactors for H<sub>2</sub> Generation

A relatively unexplored\nenergy source in synthetic cells\nis transmembrane\nelectron transport, which like proton and ion transport can be light\ndriven. Here, synthetic cells, called nanoreactors, are engineered\nfor compartmentalized, semiartificial photosynthetic H<sub>2</sub> production by a <i>Clostridium beijerinckii</i> [FeFe]-hydrogenase\n(H<sub>2</sub>ase). Transmembrane electron transfer into the nanoreactor\nwas enabled by MtrCAB, a multiheme transmembrane protein from <i>Shewanella oneidensis</i> MR-1. On illumination, graphitic nitrogen-doped\ncarbon dots (g-N-CDs) outside the nanoreactor generated and delivered\nphotoenergized electrons to MtrCAB, which transferred these electrons\nto encapsulated H<sub>2</sub>ase without requiring redox mediators.\nCompartmentalized, light-driven H<sub>2</sub> production was observed\nwith a turnover frequency (TOF<sub>H2ase</sub>) of 467 ± 64 h<sup>–1</sup> determined in the first 2 h. Addition of the redox\nmediator methyl viologen (MV) increased TOF<sub>H2ase</sub> to 880\n± 154 h<sup>–1</sup>. We hypothesize that the energetically\n“uphill” electron transfer step from MtrCAB to H<sub>2</sub>ase ultimately limits the catalytic rate. These nanoreactors\nprovide a scaffold to compartmentalize redox half reactions in semiartificial\nphotosynthesis and inform on the engineering of nanoparticle–microbe\nhybrid systems for solar-to-chemical conversion.