Efficient CO₂ Hydrogenation to Formate with Immobilized Ir‐Catalysts Based on Mesoporous Silica Beads

Abstract

The Nozaki Ir-based CO 2 hydrogenation catalyst was successfully immobilized on post-functionalized silica beads (d = 200 mm) through click chemistry.T his material hydrogenatesC O 2 into formic acid with turnover numbers reaching 2.8 10 4 in ab atch reactor within 24 hours, paving the way towards the design of efficient heterogeneous catalysts for this transformation.

Heterogeneous catalysts for CO2hydrogenation to formic acid/formate: from nanoscale to single atom

“…35 Herein, we will mainly focus on the latest findings on developing novel metal oxide-based SACs. Recently, the group of Copéret developed two pincer-type metal complexes grafted on silica with high efficiencies by means of click reaction, 165,166 namely, azide-alkyne cycloaddition. As shown in Figure 19A and B, a Ru(II) complex containing NHC ligand was successfully anchored to mesoporous silica (SBA) by three steps: (1) incorporating NHC pincer ligand via click reaction; (2) passivating the surface of SBA to avoid side reactions when introducing Ru complex; and (3) the incorporation of RuHCl(CO)(PPh 3 ) 3 .…”

“…The origin of enhanced activity upon heterogenization remained unclear. In a similar way, a highly reactive Ir−PPh pincer complex was grafted onto mesoporous silica beads (MSB) (Figure 19C), 165 giving a high TON of 28000 within 24 h at 150 °C and 50 bar CO 2 /H 2 (1/1) (Table 3, entry 17). However, both catalysts exhibited poor stabilities with pronounced drops of TONs during recycling tests, probably owing to the unstable Si−O−Si linkage between silica and metal complexes under basic conditions.…”

Recent Developments in the Modelling of Heterogeneous Catalysts for CO2 Conversion to Chemicals

“…The most commonly used catalysts for the conversion of CO 2 into formic acid are precious metals Rh, [159,160] Ru, [161] Ir, [160,162] Pd [163] as they contain homogeneous ligands, such as phosphine ligands, [164] pincer ligands, [164] N-heterocyclic carbene ligands, [164] proton-responsive ligands. [165,166] However, the synthesis of these homogenous catalysts is complicated along with high energy consumption.…”

“…The most commonly used catalysts for the conversion of CO 2 into formic acid are precious metals Rh, Ru, Ir, Pd as they contain homogeneous ligands, such as phosphine ligands, pincer ligands, N‐heterocyclic carbene ligands, proton‐responsive ligands …”

Highly Active Ir/In2O3 Catalysts for Selective Hydrogenation of CO2 to Methanol: Experimental and Theoretical Studies

“…On the other hand, the organic iridium (Ir) complex has been extensively confirmed to be a highly active catalyst for homogeneous CO 2 hydrogenation to formate, ,− which was considered for reversible hydrogen storage. − The Ir complex also showed a good activity for CO 2 photocatalytic conversion. , However, only a few works can be found in the literature with the use of a heterogeneous Ir-based catalyst for CO 2 conversion. − The high surface energy of small Ir nanoparticles thermodynamically makes them unstable and impels them to form larger particles when exposed at elevated temperatures . In order to stabilize the Ir nanoparticles, a very effective method is to find an ideal supporting material with strong interaction with Ir. ,, With this strong metal–support interaction, one can even be able to tune the selectivity of CO 2 hydrogenation over Ir/CeO 2 and Ir/TiO 2 catalysts from methane to carbon monoxide. , A bifunctional Ir 1 –In 2 O 3 single-atom catalyst was developed very recently by anchoring the monatomic Ir onto the In 2 O 3 carrier .…”