Conversion of Formic Acid into Methanol Using a Bipyridine-Functionalized Molecular Heterogeneous Catalyst

Abstract

Although the conversion of carbon dioxide (and its derivatives) into methanol has attracted remarkable attention in the last two decades, performing this process over a heterogeneous catalyst under mild conditions is still a challenging task. We report bipyridine-functionalized iridium-based heterogeneous catalysts for the hydrogenation of formic acid to produce methanol at low temperature. The solid catalysts were obtained by post-synthetic metalation of bipyridine-functionalized organosilica nanotubes with a [Cp*Ir(H2O)3]SO4 (Cp* = η 5-pentamethylcyclopentadienyl) complex. Detailed studies including N2 adsorption, TEM, XPS, and 13 C CP MAS NMR confirmed the stable structures of nanotube supports and the molecular nature of the active species. The catalysts showed competitive methanol selectivities compared to their homogeneous counterpart under similar reaction conditions. Addition of strong acids (such as triflic acid) showed improved methanol selectivity, whereas the presence of free bipyridine groups was found to promote the dehydrogenation of formic acid, resulting in low methanol selectivity. The catalyst showed excellent reusability over four consecutive cycles without any significant loss in activity and maintained its heterogeneous nature in extremely high acidic environment.

Highly Stable N-Doped Carbon-Supported Pd-Based Catalysts Prepared from Biomass Waste for H2 Production from Formic Acid

“…As for the role of formic acid in the energy scenario, it can be either used as a fuel in direct formic acid fuel cells (DFAFCs) or in the production of hydrogen, as a liquid organic hydrogen carrier molecule . Moreover, formic acid can be also used to produce other fuels and fuel intermediates, such as γ-valerolactone and methanol. ,, Among those options, its advantages as a hydrogen carrier molecule have been widely studied. − Formic acid is the simplest carboxylic acid (HCOOH), and it has a volumetric hydrogen capacity of ∼53.4 g L –1 , equivalent to 4.4 wt % H 2 , which is very close to the value set by the US Department of Energy for efficient H 2 storage substances for light-duty fuel cell vehicles. ,, The dehydrogenation of formic acid into H 2 can take place under mild conditions provided that suitable metal catalysts are used. Among those investigated options, heterogeneous Pd-based catalysts have been reported to be the most promising option; however, most of the systems lack stability under reaction conditions, which is one of the most important drawbacks. ,− Carbon materials are the preferred supports to develop efficient catalysts to boost the generation of hydrogen from formic acid, offering large surface area and surface functional groups that serve as the anchoring points of metal nanoparticles.…”

Functionalized Silicas for Metal‐Free and Metal‐Based Catalytic Applications: A Review in Perspective of Green Chemistry

“…Except the above‐discussed functionalities, the other functional groups such as glycidyloxy, azido, isocyanate, cyano, vinyl, pyridyl substituted thioether, pyridyl, carboxylic acid, and phosphonate groups are grafted on silica through the condensation with the corresponding organosilanes. J. T. Sarmiento et al.…”

“…Furthermore, OSs provide the facile mass transfer for the reactants as well as the products during the catalysis . Recently, a list of organosilanes is reported for the preparation of OSs which includes 1,4‐bis(triethoxysilyl)benzene, 4,4′‐bis(triisopropoxysilyl)‐2,2′‐bipyridine, 1,2‐bis(triethoxysilyl)ethane, tris[3‐(trimethoxysilyl)propyl] isocyanurate, 1,3‐bis(3‐trimethoxysilylpropyl)‐imidazolium iodide and 4,4′‐[4‐(trimethoxysilanyl)butyl]‐2,2′‐bipyridine . These organosilanes evidence that OSs can possess the organic groups such as ionic liquids and bipyridyl rather than just having phenyl and ethyl groups.…”

“…For the reduction reactions, FS‐based noble metal catalysts are preferential however the non‐noble metal catalysts immobilized on FS are also recently utilized . To investigate the catalytic efficacy of metal NPs in reduction reactions, p ‐nitrophenol reduction to p ‐aminophenol has been employed as the model reaction .…”

Mechanism of Formic Acid Disproportionation Catalyzed by an Iridium Complex Immobilized on Bipyridine‐Periodic Mesoporous Organosilica: A Case Study Based on Kinetics Analysis

“…The disproportionation of FA is not good in terms of the atom efficiency compared to the direct CO 2 hydrogenation, while the energy efficiency is higher because the reaction is carried out under lower pressure and temperature. Although there have been many reports concerning FA disproportionation using different homogeneous Ir‐2,2′‐bipyridine (BPy) complexes, the application of heterogeneous catalysts is an indispensable prerequisite for the development of industrial MeOH production …”