Fluorinated chlorin chromophores for red-light-driven CO2 reduction.

The utilization of low-energy photons in light-driven reactions is an effective strategy for improving the efficiency of solar energy conversion. In nature, photosynthetic organisms use chlorophylls to harvest the red portion of sunlight, which ultimately drives the reduction of CO2. However, a molecular system that mimics such function is extremely rare in non-noble-metal catalysis. Here we report a series of synthetic fluorinated chlorins as biomimetic chromophores for CO2 reduction, which catalytically produces CO under both 630 nm and 730 nm light irradiation, with turnover numbers of 1790 and 510, respectively. Under appropriate conditions, the system lasts over 240 h and stays active under 1% concentration of CO2. Mechanistic studies reveal that chlorin and chlorinphlorin are two key intermediates in red-light-driven CO2 reduction, while corresponding porphyrin and bacteriochlorin are much less active forms of chromophores.

Pyridinethiolate-Capped CdSe Quantum Dots for Red-Light-Driven H2 Production in Water.

The utilization of low-energy sunlight to produce renewable fuels is a subject of great interest. Here we report the first example of metal chalcogenide quantum dots (QDs) capped with a pyridinethiolate carboxylic acid (pyS-COOH) for red-light-driven H2 production in water. The precious-metal-free system is robust over 240 h, and achieves a turnover number (TON) of 43910 ± 305 (vs Ni) with a rate of 31570 ± 1690 mmol g-1 h-1 for hydrogen production. In contrast to the inactive QDs capped with other thiolate ligands, the CdSe-pyS-COOH QDs give a significantly higher singlet oxygen quantum yield [ΦΔ (1O2)] in solution.

Efficient Red-Light-Driven Hydrogen Evolution with an Anthraquinone Organic Dye.

The direct utilization of the full solar spectrum to obtain renewable fuels remains a challenge because the conversion of the low-energy light (red and near-infrared) is difficult. Current light-driven systems show activity for hydrogen generation with the high-energy part of sunlight. Here we report the use of a simple anthraquinone organic dye in an artificial photosynthetic system that promotes efficient red-light-driven production of hydrogen. The system contains no noble metal and exhibits a turnover number greater than 0.78 million and a quantum yield of 30.6% at 630 nm. A mechanistic study revealed that the excited-state and redox properties of the chromophore are critical to achieving high activity and stability.