Chemoenzymatic Hydrogen Production from Methanol through the Interplay of Metal Complexes and Biocatalysts

Abstract

Microbial methylotrophic organisms can serve as great inspiration in the development of biomimetic strategies for the dehydrogenative conversion of C1 molecules under ambient conditions. In this Concept article, a concise personal perspective on the recent advancements in the field of biomimetic catalytic models for methanol and formaldehyde conversion, in the presence and absence of enzymes and co‐factors, towards the formation of hydrogen under ambient conditions is given. In particular, formaldehyde dehydrogenase mimics have been introduced in stand‐alone C1‐interconversion networks. Recently, coupled systems with alcohol oxidase and dehydrogenase enzymes have been also developed for in situ formation and decomposition of formaldehyde and/or reduced/oxidized nicotinamide adenine dinucleotide (NADH/ NAD+). Although C1 molecules are already used in many industries for hydrogen production, these conceptual bioinspired low‐temperature energy conversion processes may lead one day to more efficient energy storage systems enabling renewable and sustainable hydrogen generation for hydrogen fuel cells under ambient conditions using C1 molecules as fuels for mobile and miniaturized energy storage solutions in which harsh conditions like those in industrial plants are not applicable.

Ruthenium‐Catalyzed E‐Selective Partial Hydrogenation of Alkynes under Transfer‐Hydrogenation Conditions using Paraformaldehyde as Hydrogen Source

“…To adjust the pH of the reaction media, addition of bases, such as amines is frequently inevitable. To overcome the problem of acidity of formic acid in such reactions, application of methanediol produced from formaldehyde in aqueous solutions could be suitable since it is less acidic and therefore, applicable for acid sensitive substrates and reactions under base‐free conditions [58–60,62–64] …”

“…Recently, the number of reports on the use of C1 molecules such as formic acid, [21][22]24,26,28,30,[37][38][54][55][56][57] formaldehyde, [58][59][60][61] and methanol [62] as hydrogen sources in transfer-hydrogenation reactions are increasing. Although it has been considered frequently as an inexpensive and safer substitute for pressurized hydrogen gas [58,63] in transfer hydrogenations and reductions, formic acid suffers from some drawbacks.…”

“…To overcome the problem of acidity of formic acid in such reactions, application of methanediol produced from formaldehyde in aqueous solutions could be suitable since it is less acidic and therefore, applicable for acid sensitive substrates and reactions under base-free conditions. [58][59][60][62][63][64] In continuation of our work to generate dihydrogen from aqueous formaldehyde, [65][66] or in situ generated aqueous formaldehyde from methanol [62] and paraformaldehyde (pFA) [66] for hydrogenations or as energy carrier, we have also used these hydrogen sources in combination with [Ru(p-cymene)Cl 2 ] as pre-catalyst for transfer hydrogenation of alkenes (with methanol), [62] for formaldehyde dismutation (with pFA in water), [67] for reductive methylation (with pFA in water) [61] and most recently for reductive deamination of nitriles to alcohols (with pFA in water). [58] In terms of practical aspects, it turned out that the easy-to-handle non-volatile paraformaldehyde (oligomeric solid powder) is very convenient in comparison to the volatile C1-molecule competitors, methanol, aqueous formaldehyde and formic acid, while the hydrogen content of pFA is equal to formaldehyde referring to the monomer.…”

Preparation and application of solvent-free liquid proteins with enhanced thermal and anhydrous stabilities

“…26,27 Given the apparent gulf between the potential capabilities of enzyme engineering and the currently niche role of biocatalysis in industrial settings, there remains an impetus to develop universal approaches to stabilizing proteins against nonaqueous environments. There have been many exciting innovations in the development of chemoenzymatic cascades [28][29][30][31] , unnatural photoenzymatic pathways [32][33][34] , and electrobiocatalysis 35,36 . The co-deployment of enzymes and abiological reactions will ultimately have greater applicability in non-aqueous solvents.…”

Low‐Temperature Methanol‐Water Reforming Over Alcohol Dehydrogenase and Immobilized Ruthenium Complex

“…The novel consecutive process is partly similar to the hydrogen production from methanol partial‐oxidation. Bioinduced reaction is a relatively novel strategy to realize hydrogen production from methanol‐water reforming at room temperature [28] . More importantly, no oxygen, alkali, or extra energy is involved under the mild conditions.…”