CO₂ Hydrogenation to Formate with Immobilized Ru‐Catalysts Based on Hybrid Organo‐Silica Mesostructured Materials

Abstract

The hydrogenation of CO2 to formic acid can be carried out by numerous homogenous catalysts, while efficient heterogeneous catalysts are rare. In this work, we successfully synthesize an immobilized lutidine‐derived pincer‐type N‐heterocyclic carbene ruthenium complex based on a mesoporous organo‐silica hybrid material using sol‐gel direct synthesis in the presence of structure directing agents and click chemistry as the two key pillars of this strategy. This material efficiently catalyzes the hydrogenation of CO2 into formate with turnover numbers reaching 18′000 within 24 hours, surpassing the performance of the corresponding homogeneous complexes.

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, Ru, Ir, Pd as they contain homogeneous ligands, such as phosphine ligands, pincer ligands, N‐heterocyclic carbene ligands, proton‐responsive ligands …”

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

“…[6c, 7] Previously,a lthough we have shown that efficient immobilized catalysts can be prepared through the post-functionalization of mesostructured hybrid organosilica materials (e.g.,alutidine-derived Ru-CNC pincer complex [3h] that achieves aT ON of 1. 8 10 4 in the CO 2 hydrogenation to formate [8] ), the utility of these SBA-type materials is limited by the texture of the support, that is, powder with small particle size (d = 10 mm), which renders filtration or usei np lug flow reactor challenging. [9] Here, we report the synthesis of am olecularly defined and highly active Ir phosphine-pincer complex supported on mesostructured porouss ilica beads (diameter = 200 mm, Figure 1).…”

Recent Progress with Pincer Transition Metal Catalysts for Sustainability

“…It was demonstrated that the method improves the stability of the catalyst compared to the homogeneous analogue, which afforded a TON of 9250 after 24 h under the same reaction conditions. Recently, Copéret demonstrated the synthesis of an immobilized lutidine-derived pincer type N-heterocyclic carbene ruthenium on a highly ordered silica-based material [651]. Complex 88 was used as catalyst for CO 2 hydrogenation into the corresponding formic acid-base adduct affording a TON of 18,000 in 24 h (Scheme 75).…”

“…Eight equivalents of ammonia per catalyst were produced when dinitrogen reacted with a reductant and a proton source at room temperature under Scheme 75. Catalyst 88 immobilized on silica material for the hydrogenation of carbon dioxide to formate salts showed by Copéret [651].…”