Ruthenium Metal–Organic Frameworks as Stable Nanostructures for Selective Hydrogen Production from Acetaldehyde and Water under Mild Conditions

Abstract

Hydrogen is a promising energy carrier because it is a wide and sustainable source. However, it is still extremely difficult to store and transport hydrogen safely because of its active chemical properties and harsh explosion limits. Organic liquid is a popular research field for hydrogen production and storage. Inspired by its biological metabolism, here acetaldehyde is innovatively used for hydrogen production. The hydrogen content of an acetaldehyde–water solution is 10.2 wt %, which is slightly lower than that of a methanol–water solution but much higher than that of formic acid and formaldehyde. For the first time, we prepared several ruthenium metal–organic frameworks (MOFs) as stable nanostructures for selective hydrogen production from acetaldehyde and water under mild conditions (∼60 °C). Ru-MOFs all have nanoscale pores, and the turnover frequency of ruthenium 2,3,5,6-tetramethyl-1,4-phenylenediamine for acetaldehyde decomposition is up to 223 h–1 in water at 90 °C. Because C–C bond cleavage is an inevitable step for hydrogen or energy production from C2 organics, ion chromatography, high-performance liquid chromatography, 1H NMR spectroscopy, and mass spectrometry were employed to propose a catalytic process of hydrogen production from acetaldehyde decomposition. We evidently prove that water participates in acetaldehyde decomposition, thereby claiming an acetaldehyde–water reforming process. Additionally, we confirm that formic acid and acetic acid are the intermediates during the hydrogen production process. This research not only holds great promise for hydrogen production from C2 organics at low temperatures, as well as catalytic technology for C–C bond cleavage, but it also provides certain profound scientific insights for hydrogen or energy production from multicarbon organics, such as biomass.