Stable Engineered Trimetallic Oxide Scaffold as a Catalyst for Enhanced Solvent-Free Conversion of CO₂ into Value-Added Products

Abstract

This work demonstrates the development of mesoporous trimetallic oxide scaffolds (TOSs) as heterogeneous catalysts for the solvent-free transformation of CO2 into various value-added products. The TOS catalyst was prepared using a solution-combustion protocol as a time- and energy-saving method using cobalt, magnesium, and cerium metal nitrate salts as precursors and ethylene glycol as the fuel system and compared with their monometallic counterparts. Characterization suggested strong metal–metal and metal–oxygen interactions in the 3D-interconnected hierarchical porous network, which resulted in substantial alteration in the electronic, structural, and physicochemical properties. This resulted in an appreciable surface area, acid–base cooperative sites, and a larger pore volume in the catalyst. Thereafter, the CoMgCe-TOS catalyst was first used for the solvent-free cyclization of o-phenylenediamines and CO2 to produce benzimidazoles. In the presence of dimethylamine borane as a reductant, benzimidazoles were obtained in 94% yield at 100 °C under pressurized conditions, along with good recyclability for 12 cycles. It was established that selectivity toward benzimidazole improved upon the incorporation of basic metals (Mg and Ce), with Co aiding in the formation of cooperative Lewis acid–base sites. A plausible mechanism was also predicted, wherein the overall conversion of reactants for the N-formylation step was influenced by the number and strength of basic sites, and the cyclization step for selectively obtaining benzimidazole was affected by the acidic site strength. Besides the production of benzimidazole, the catalyst was also highly active for the synthesis of cyclic carbonates using epoxides and CO2 under optimized reaction conditions. This work therefore provides a new and greener route for the synthesis of benzimidazoles and organic carbonates, which can be easily adapted for scale-up applications.

Trimetallic Oxide Foam as an Efficient Catalyst for Fixation of CO2 into Oxazolidinone: An Experimental and Theoretical Approach

“…As mentioned in Table , Comparing different metal ratios of trimetallic, bimetallic, and monometallic oxide catalysts for CO 2 fixation, the PTOF trimetallic catalyst achieved excellent results under optimized reaction conditions. Earlier reports well emphasized that the catalysts containing mixed metal oxide phases and related systems showed efficient potential for the catalytic activity . Wang et al reported that abundant multimixed metal oxide phases and their surface showed excellent catalytic activity than the bimetallic and monometallic oxide counterparts toward catalytic transformation .…”

“…Earlier reports well emphasized that the catalysts containing mixed metal oxide phases and related systems showed efficient potential for the catalytic activity. 29 Wang et al reported that abundant multimixed metal oxide phases and their surface showed excellent catalytic activity than the bimetallic and monometallic oxide counterparts toward catalytic transformation. 56 Remarkably, the mixed metal oxide catalytic systems will attain a more synergistic effect compared to the bimetallic and monometallic oxides under suitable reaction conditions.…”

“…This rapid combustion methodology benefits the formation of highly porous morphology, good crystalline phases with surface properties, and importantly excellent surface active sites on the materials. 28,29 The exhausted gases cool the as-combusted products and prevent the sintering effect during catalyst synthesis. 30 Herein, we demonstrated effective fixation of CO 2 into oxazolidinone using propylene oxide and aniline as substrates catalyzed by the efficient PTOF.…”

“…The molecular mixing of the fuel and oxidizer together upon combustion releases an enormous amount of gases such as CO, CO 2 , NO, H 2 , and N 2 . This rapid combustion methodology benefits the formation of highly porous morphology, good crystalline phases with surface properties, and importantly excellent surface active sites on the materials. , The exhausted gases cool the as-combusted products and prevent the sintering effect during catalyst synthesis …”

Base-Tailored Hierarchical MgO Microspheres as Efficient Catalysts for CO2 Fixation into Oxazolidinone at Atmospheric Pressure

“…In Figure 2 (30−32), images are observed of more aggregation of particles with the reduction of surface smoothness. Hence, the CC-MgO surface is observed to exhibit a higher particle aggregation with irregular nanoflake morphology, as shown in Figure 2 (32). From this in-depth discussion, it is observed that precipitating agents significantly played a very decisive role to obtain uniform 3D microsphere morphology of MgO materials.…”