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

Abstract

The excess anthropogenic CO 2 depletion via the catalytic approach to produce valuable chemicals is an industrially challenging, demanding, and encouraging strategy for CO 2 fixation. Herein, we demonstrate a selective one-pot strategy for CO 2 fixation into "oxazolidinone" by employing stable porous trimetallic oxide foam (PTOF) as a new catalyst. The PTOF catalyst was synthesized by a solution combustion method using transition metals Cu, Co, and Ni and systematically characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), N 2 sorption, temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS) analysis. Due to the distinctive synthesis method and unique combination of metal oxides and their percentage, the PTOF catalyst displayed highly interconnected porous channels along with uniformly distributed active sites on its surface. Well ahead, the PTOF catalyst was screened for the fixation of CO 2 into oxazolidinone. The screened and optimized reaction parameters revealed that the PTOF catalyst showed highly efficient and selective activity with 100% conversion of aniline along with 96% selectivity and yield toward the oxazolidinone product at mild and solvent-free reaction conditions. The superiority of the catalytic performance could be due to the presence of surface active sites and acid−base cooperative synergistic properties of the mixed metal oxides. A doubly synergistic plausible reaction mechanism was proposed for the oxazolidinone synthesis experimentally with the support of DFT calculations along with bond lengths, bond angles, and binding energies. In addition, stepwise intermediate formations with the free energy profile were also proposed. Also, the PTOF catalyst displayed good tolerance toward substituted aromatic amines and terminal epoxides for the fixation of CO 2 into oxazolidinones. Very interestingly, the PTOF catalyst could be significantly reused for up to 15 consecutive cycles with stable activity and retention in physicochemical properties.

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

“…2− and other impurities, as displayed in Figure 2 (13). In higher magnification images, the aggregation of irregular microflakes (Figure 2 (14,15)) is evidently noticed with a layered fashion, and importantly, flakes do not have any explicit morphology, as clearly displayed in Figure 2 (16).…”

“…Interestingly, the achieved inherent properties strongly enhanced Lewis acidic and basic site concentrations in the catalyst and are also easily accessible on the catalytic surface during the oxazolidinone reaction. 16,22 3.6. Substrate Scope Study over Hierarchical SC-MgO Microsphere Catalyst for CO 2 Fixation Reaction.…”

“…Previously, we reported the plausible oxazolidinone reaction mechanism with the support of both experimental and theoretical results. 16 The uniformly disseminated SC-MgO catalyst active sites enhanced the initial reagents of epoxide and carbon dioxide activation in the reaction medium. As shown in Scheme 2 and in Step 1, unactivated molecules of styrene oxide and CO 2 molecules are successfully activated with the help of Lewis acidic (Mg + ) and Lewis basic (O 2− ) sites, respectively.…”

“…56 In Step 8, the activated epoxide molecule interacted with the carbonyl carbon of the phenyl isocyanate and produced the unstabilized desired product of oxazolidinone (Step 9) via the intermolecular cyclization process. 16 Finally, the stable molecule of the oxazolidinone product was successfully obtained (Step 10) by the elimination of the SC-MgO catalyst surface. Later, the same catalyst surface begins as the active catalyst surface (Step 11) in the reaction mechanism.…”

“…15 For the oxazolidinone synthesis, previously nonrecyclable and recyclable catalysts were reported, which suffered few negatives. 16 Thus, the design of the promised robust catalyst is more essential for this protocol. In earlier reports, catalyst synthesis procedures were little tedious, toxic solvents were used, and reactions were performed under high pressure and temperature, under solvent and cocatalyst conditions, and, more importantly, nonrecyclable featured catalysts.…”