High-Rate Hydrogen Generation by Direct Sunlight Irradiation with a Triruthenium Complex

Abstract

Herein we report a biomimetic triruthenium catalyst that, when under direct sunlight irradiation, facilitates high-rate H 2 production from formic acid (FA) dehydrogenation. The system consists of 2 μmol of catalyst and 6 μmol of tri-otolylphosphine in 1 mL of dimethylformamide (DMF) and 4 mL of FA/triethylamine (TEA; 5:2). With 0.4 mM catalyst loaded, a high turnover frequency of 1.15 × 10 6 h −1 was detected when under direct sunlight irradiation. In an experiment with 0.2 mM catalyst loaded, more than 140 L of H 2 (280 L of H 2 + CO 2 ) was produced, and a turnover number of approximately 2.78 × 10 6 was obtained within 5 h without decline in H 2 generation activity, making it suitable for high-rate H 2 production.

Efficient and Reversible Catalysis of Formic Acid‐Carbon Dioxide Cycle Using Carbamate‐Substituted Ruthenium‐Dithiolate Complexes

“…We recently reported that amido‐bis(S)‐substituted triruthenium biomimetic H‐cluster complex exhibits high FA dehydrogenation efficiency under conditions of direct sunlight irradiation. Under these conditions, a TON of ∼2.78×10 6 and a TOF of ∼1.15×10 6 h −1 were recorded [2] . Inspired by the above results and keeping in mind the long‐term goals of establishing a complete “carbon neutral cycle” to reversibly convert FA to CO 2 /H 2 and CO 2 /H 2 to FA, we explored the efficiency of this series of bionics to catalyze the reduction of CO 2 to FA.…”

“…This method can be used to produce H 2 on a commercial scale. Thus, it is possible to produce H 2 in the absence of an external power source to realize on‐site commercial and industrial applications [2] …”

“…Later, it was also reported that iridium and ruthenium complexes derived from N ‐heterocyclic carbenes and pyridinols can reversibly catalyze the FA‐CO 2 /H 2 cycle [9] . Our group has been developing homogeneous catalysts using Ru‐based biomimetic H‐cluster systems for FA dehydrogenation [2,10] . We recently reported that amido‐bis(S)‐substituted triruthenium biomimetic H‐cluster complex exhibits high FA dehydrogenation efficiency under conditions of direct sunlight irradiation.…”

“…The synthesis of carbamate‐substituted ruthenium dithiolate complexes was carried out by reacting Ru 3 (CO) 12 with tert ‐butyl (1,2‐dithiolan‐4‐yl)carbamate in tetrahydrofuran (THF) under an atmosphere of Ar. Previously reported protocols were slightly modified (reaction time was fixed to be 4 h) to carry out the reactions [2] . Three complexes were obtained, and their structures were determined using the 1 H nuclear magnetic resonance (NMR) spectroscopy, 13 C NMR spectroscopy, and mass spectrometry techniques.…”

“…The complexes were identified to be [Ru 2 (CO) 6 (μ‐SCH(NCO 2 (C(CH 3 ) 3 ))CH 2 CH 2 S)] ( 1 ), [Ru 3 (CO) 9 (μ‐SCH(NCO 2 (C(CH 3 ) 3 ))CH 2 CH 2 S)] ( 2 ), and [Ru 6 (CO) 20 (μ‐SCH(NCO 2 (C(CH 3 ) 3 ))CH 2 CH 2 S)] ( 3 ) (Figure 2, Figure S1–S3). The structures of complexes 1 and 2 have been previously determined [2] . The Ru(1)‐Ru(2) distance [2.6763 Å] in complex 1 is shorter than the Ru(1)‐Ru(2) [2.8021 Å] distance in complex 2 , indicating that the bridging dithiolate ligand generates an unfavorable constrained environment for the dimetal in 1 [12] .…”