Dehydrogenation of anhydrous methanol at room temperature by o-aminophenol-based photocatalysts

Abstract

Dehydrogenation of anhydrous methanol is of great importance, given its ubiquity as an intermediate for the production of a large number of industrial chemicals. Since dehydrogenation of methanol is an endothermic reaction, heterogeneous or homogeneous precious-metal-based catalysts and high temperatures are usually required for this reaction to proceed. Here we report the photochemical dehydrogenation of anhydrous methanol at room temperature catalysed by o-aminophenol (apH2), o-aminophenolate (apH−) and the non-precious metal complex trans-[FeII(apH)2(MeOH)2]. Under excitation at 289±10 nm and in the absence of additional photosensitizers, these photocatalysts generate hydrogen and formaldehyde from anhydrous methanol with external quantum yields of 2.9±0.15%, 3.7±0.19% and 4.8±0.24%, respectively, which are the highest values reported so far to the best of our knowledge. Mechanistic investigations reveal that the photo-induced formation of hydrogen radicals triggers the reaction.

Direct Photochemical C–H Carboxylation of Aromatic Diamines with CO2 under Electron-Donor- and Base-free Conditions

“…On the other hand, we found that the new signals emerged at 0.88, 0.89, and 1.19 ppm in the 1 H NMR spectrum of a THF- d 8 solution of t -Bu 2 S 2 after photo-irradiation ( λ ex = 300 ± 10 nm), which demonstrates the photoreactivity of t -Bu 2 S 2 (Fig. 4c ) 63 . These resonances are thus indicative of the in-situ formation of t -Bu 2 S 2 .…”

“…Subsequently, we attempted to identify the active species by trapping experiments. It was previously reported that 2-methylpropane-2-thiol ( t -BuSH) can act as a hydrogen (H) radical scavenger forming di- tert -butyl disulfide ( t -Bu 2 S 2 ) 63 , 64 . The detection of t -Bu 2 S 2 among the photochemical reaction products of opda and 1 revealed the H radical generation during the reaction ( vide infra ).…”

Low-temperature hydrogen production from methanol over a ruthenium catalyst in water

“…11 Beller and other researchers also highlighted the role of waterpromoted dehydrogenation of formaldehyde to formic acid and H 2 during the methanol dehydrogenation reaction. 25,38 Notably, Lin et al also reported efficient hydrogen production from methanol over Pt/α-MoC with a higher water content (CH 3 OH/H 2 O molar ratio of 1 : 3 and 1 : 1). 35 Notably, we found that the base played a crucial role in generating the active Ru nanoparticles in the initial hour of the reaction.…”

Homogeneous Catalysis for Sustainable Hydrogen Storage in Formic Acid and Alcohols

“…Another Fe photocatalyst was applied by Chang and co-workers in which the metal complex trans -[Fe II (apH) 2 (MeOH) 2 ] (apH = o -aminophenolato ligand) ( 89 ) was able to promote anhydrous methanol dehydrogenation at room temperature without the need for additional photosensitizers . Mechanistic studies suggested that hydrogen radicals induced by photocatalysis trigger this hydrogen evolution reaction.…”