Paving way for sustainable earth-abundant metal based catalysts for chemical fixation of CO2 into epoxides for cyclic carbonate formation

Aerobic Oxidative Carboxylation of Styrene Over Cobalt Catalysts: Integrated CO2 Capture and Conversion

The direct synthesis of cyclic carbonates through oxidative carboxylation of alkenes using CO2 and O2 offers a sustainable and carbon-neutral method for CO2 utilization, which is, however, still a largely unexplored field. Here we develop a single-atom catalyst (SAC) Co-N/O-C as the earth-abundant metal catalyst for the oxidative carboxylation of styrene with CO2 and O2. Remarkably, even using the flue gas as an impure CO2 and O2 source, desired cyclic carbonate could be obtained with moderate productivity, which shows the potential for integrated CO2 capture and conversion, leveraging the high CO2 adsorption capacity of Co-N/O-C. In addition, the catalyst can be reused five times without an obvious decline in activity. Detailed characterizations and theoretical calculations elucidate the crucial role of single Co atoms in activating O2 and CO2, as well as controlling selectivity.

Synthesis of Trimetallic Nanoparticle (NiCoPd)-Supported Carbon Nanofibers as a Catalyst for NaBH4 Hydrolysis

The generation of H2 via the catalytic hydrolysis of sodium borohydride (SBH) has promise as a practical and secure approach to produce H2, a secure and environmentally friendly energy source for the foreseeable future. In this study, distinctive trimetallic NiCoPd nanoparticle-supported carbon nanofibers (NiCoPd tri-NPs@CNFs) is synthesized via sol-gel and electrospinning approaches. The fabricated trimetallic catalysts show an excellent catalytic performance for the generation of H2 from the hydrolysis of SBH. Standard physicochemical techniques were used to characterize the as-prepared NiCoPd tri-NPs@CNFs. The results show that NiCoPd tri-NPs@CNFs is formed, with an average particle size of about 21 nm. When compared to NiCo bimetallic NP @CNFS, all NiCoPd tri-NPs@CNFs formulations demonstrated greater catalytic activates for the hydrolysis of SBH. The improved catalytic activity may be due in the majority to the synergistic interaction between the three metals in the trimetallic architecture. Furthermore, the activation energy for the catalytic hydrolysis of SBH by the NiCoPd tri-NPs@CNFs was determined to be 16.30 kJ mol-1. The kinetics studies show that the reaction is of a first order with respect to the catalyst loading amount and a half order with respect to the SBH concentration [SBH].

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

The excess anthropogenic CO₂ depletion via the catalytic approach to produce valuable chemicals is an industrially challenging, demanding, and encouraging strategy for CO₂ fixation. Herein, we demonstrate a selective one-pot strategy for CO₂ 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), N₂ 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 CO₂ 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 CO₂ 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.

Designing of 3D Architecture Flower-like Mn-Promoted MgO and Its Application for CO2 Adsorption and CO2-Assisted Aerobic Oxidation of Alkylbenzenes

Sustainable chemistry research prioritizes reducing atmospheric carbon dioxide, and one logical solution is to develop adsorbents suitable for carbon capture and utilization. In this work, a new family of three-dimensional (3D) flower-like Mn-promoted MgO was synthesized by the coprecipitation method and used as an adsorbent for CO₂ capture and a catalyst for CO₂ utilization. The scanning electron microscopy (SEM) analysis of the samples shows a 3D architecture composed of thin nanosheets. The X-ray diffraction (XRD) analysis confirms the presence of the MgO with a cubic structure, while X-ray photoelectron spectroscopy (XPS) reveals the existence of Mn particles as a combination of Mn³⁺ and Mn⁴⁺ ions on MgO. N₂ adsorption-desorption experiments highlight the beneficial contribution of Mn particles to surface area enhancement and reveal the existence of mesopores. Furthermore, the designed 3D Mn-doped MgO as an adsorbent demonstrates its capability to improve the ability of MgO to adsorb CO₂ (from 0.28 mmol/g for pure MgO to 0.74 mmol/g) in ambient conditions and it is regenerable up to 9 cycles with a slight variation after the third cycle. Moreover, Mn-doped MgO shows good catalyst activity for the oxidation of ethylbenzene derivatives to carbonyl compounds in the presence of CO₂ and O₂. Mn-15/MgO shows excellent catalytic behavior with a conversion of 97.4 and 100% selectivity. Also, it is regenerable with an insignificant decrease in conversion (∼11.63%) after seven cycles, while the selectivity of acetophenone remains stable. The analyses of the recycled sample suggest that the chemical compositions of Mn and Mg influence the catalytic activity of those Mn-promoted MgO materials. The role of CO₂ gas in the aerobic oxidation of ethylbenzene to acetophenone has also been proved. Finally, the control experiments and EPR studies reveal that the reaction takes place through the formation of radicals.

An octahedral cobalt(iii) complex based on cheap 1,2-phenylenediamine as a bifunctional metal-templated hydrogen bond donor catalyst for fixation of CO2 with epoxides under ambient conditions

An octahedral cobalt(iii) complex based on cheap 1,2-phenylenediamine operates as an efficient bifunctional hydrogen bond donor catalyst in cycloaddition of epoxides with CO₂ under ambient conditions and solvent- and co-catalyst-free conditions.

Highly Active CO2 Fixation into Cyclic Carbonates Catalyzed by Tetranuclear Aluminum Benzodiimidazole-Diylidene Adducts

A set of tetranuclear alkyl aluminum adducts 1 and 2 supported by benzodiimidazole-diylidene ligands L1, N,N’-(1,5-diisopropylbenzodiimidazole-2,6-diylidene)bis(propan-2-amine), and L2, N,N’-(1,5-dicyclohexyl-benzodiimidazole-2,6-diylidene)dicyclohexanamine were synthetized in exceptional yields and characterized by spectroscopic methods. These compounds were studied as catalysts for cyclic carbonate formation (3a–o) from their corresponding terminal epoxides (2a–o) and carbon dioxide utilizing tetrabutylammonium iodide as a nucleophile in the absence of a solvent. The experiments were carried out at 70 °C and 1 bar CO2 pressure for 24 h and adduct 1 was the most efficient catalyst for the synthesis of a large variety of monosubstituted cyclic carbonates with excellent conversions and yields.