Efficient Catalytic Decomposition of Formic Acid for the Selective Generation of H₂ and H/D Exchange with a Water‐Soluble Rhodium Complex in Aqueous Solution

Abstract

Formic acid (HCOOH) decomposes efficiently to afford H2 and CO2 selectively in the presence of a catalytic amount of a water-soluble rhodium aqua complex, [Rh(III)(Cp*)(bpy)(H2O)]2+ (Cp*=pentamethylcyclopentadienyl, bpy=2,2'-bipyridine) in aqueous solution at 298 K. No CO was produced in this catalytic decomposition of HCOOH. The decomposition rate reached a maximum value at pH 3.8. No deterioration of the catalyst was observed during the catalytic decomposition of HCOOH, and the catalytic activity remained the same for the repeated addition of HCOOH. The rhodium-hydride complex was detected as the catalytic active species that undergoes efficient H/D exchange with water. When the catalytic decomposition of HCOOH was performed in D2O, D2 was produced selectively. Such an efficient H/D exchange and the observation of a deuterium kinetic isotope effect in the catalytic decomposition of DCOOH in H2O provide valuable mechanistic insight into this efficient and selective decomposition process.

Decomposition of Formic Acid Catalyzed by a Phosphine‐Free Ruthenium Complex in a Task‐Specific Ionic Liquid

“…[1] In particular for portable applications, the use of liquid hydrogen has several disadvantages due to its continuous evaporation. Among various storage materials and methods currently under investigation, molecular hydrogen adsorption on materials of large surface area [5][6][7][8] and clathrate hydrates, [9] the use of bonded hydrogen atoms in hydrocarbons, [10] metal hydrides [11,12] or formic acid (FA) [13][14][15][16][17] show considerable promise.…”

Product Selectivity in Homogeneous Artificial Photosynthesis Using [(bpy)Rh(Cp*)X]n+-Based Catalysts

“…Since the late 1980s, the catalytically active species has been described as a Rh III -H (structure A in Figure 4) [33,45]. The experimental proof of the existence of this species has been performed by Steckhan et al [51], as well as Fukuzumi et al [60], using a 6,6′-dimethylated bipyridine [33][34][35][36][37][38], reaction (b) [39,40], reaction (c) [26,29,[41][42][43][44], reaction (d) [45][46][47][48][49][50][51][52][53][54][55], and reaction (e) [48,[56][57][58][59].…”

“…Since the late 1980s, the catalytically active species has been described as a Rh III -H (structure A in Figure 4) [33,45]. The experimental proof of the existence of this species has been performed by Steckhan et al [51], as well as Fukuzumi et al [60], using a 6,6 -dimethylated bipyridine as the N,N-chelating ligand. However, as for other sterically less demanding N,N-chelating ligands, the Rh III -H moiety has so far not been observed.…”

“…In order to use molecular hydrogen as a green fuel, efficient catalytic liberation from the storage materials is an important prerequisite for this technology. It has been shown that [(bpy)Rh(Cp*)(H2O)] 2+ is able to selectively decompose formic acid into H2 and CO2 via a rhodium formato and a rhodium hydride intermediate without the production of CO [60] [33,58,70].…”

Hidrogén tárolása homogén katalitikus kémiai rendszerekben

“…Igen nagy katalitikus aktivitást észleltek ródium 17,18 , ruténium 19 és iridium 20 26 . 2 Cl(mtppms-Na) 3 ]-katalizálta bontásával -a hõmérséklet hatása.…”