One-pot synthesized efficient molybdenum‑niobium-oxide nanocatalyst for selective C-O and C-N coupling reactions at mild conditions

Kalbande, Pavan Narayan; Singh, Nittan; Swapna, Bhattu; Umbarkar, Shubhangi; Sudarsanam, Putla

doi:10.1016/j.catcom.2023.106766

Cited by 4 publications

(4 citation statements)

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“…The d -spacing of the nanocrystals was found to be ∼0.39 nm, which belongs to the (001) plane of pseudohexagonal Nb 2 O 5. ,− But, the average size of the Nb 2 O 5 particles is about 4.2 ± 0.5 nm, which is the reason for the absence of its XRD peaks (Figure a). The EDS elemental mapping images confirm the presence of Ce, Nb, and O in the NbCeNR4 catalyst, and the Nb species are uniformly dispersed in the NbCeNR4 catalyst (Figure c).…”

Section: Resultsmentioning

confidence: 99%

“…Particularly, the NbCeNR4 catalyst exhibited very sharp peaks of both LA and BA sites. The LA + BA peak at 1481 cm –1 was not found in NbCeNR5 material, which is due to the aggregation of Nb 2 O 5 particles as well as the removal of bridged OH species at higher calcination temperatures (500 °C) . Overall, the NbCeNR4 material contains high-intensity FT-IR peaks with both Brønsted and Lewis acidic sites.…”

Section: Resultsmentioning

confidence: 99%

“…For this, the catalyst must contain adequate Lewis acid sites, which play a dual role: (a) interacting with the lone pair of −OH group of benzyl alcohol to induce oxidative dehydrogenation step in the presence of an oxidant to obtain the benzaldehyde intermediate and (b) increasing the electrophilic nature of the carbonyl carbon of benzaldehyde to stimulate its condensation with –NH 2 group of aniline or o-phenylenediamine. − The pyridine-adsorbed FT-IR studies showed that the NbCeNR4 nanocatalyst contains more Lewis acid sites than the pure CeO 2 nanorods (CeNR4) and NbCeNR5 material (Figure ). The highly dispersed Nb 2 O 5 in the NbCeNR4 nanocatalyst (Figure ) is the reason for its higher Lewis acidic strength (i.e., Nb 5+ species). ,− As shown in Figure , the activation of molecular oxygen by oxygen vacancies in the ceria lattice is crucial for the oxidative dehydrogenation of benzyl alcohol to benzaldehyde. The XPS studies confirmed that the NbCeNR4 nanocatalyst contains more Ce 3+ ions associated with the oxygen vacancies (Figure c,d), which react with molecular oxygen to generate activated oxygen, a well-known fact in the literature. − Thus, the combination of Lewis acid sites and oxygen vacancies is a key factor for the higher activity of the NbCeNR4 nanocatalyst in the C–N coupling of benzyl alcohol with aniline and o-phenylenediamine.…”

Section: Structure–activity Correlation Of Shape-controlled Nb-ceo2 N...mentioning

confidence: 99%

“…On the other hand, the Nb 2 O 5 species adsorbed on the surface of CeO 2 nanorods provided strong acid sites. The presence of unsaturated, surface Nb 5+ sites enabled Nb 2 O 5 as an effective solid acid catalyst for various organic chemical transformations. ,− Thus, the Nb-CeO 2 nanorods calcined at 400 °C for 4 h showed higher catalytic activity and selectivity in the C–N coupling of benzyl alcohol with aniline and o -phenylenediamine.…”

Section: Introductionmentioning

confidence: 99%

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Nb₂O₅/Ce_1–xNb_xO_2−δ Nanorod Catalyst for Selective Oxidative Coupling of Aromatic Alcohols and Amines

Arun Kumar,

Kamali,

Putla

et al. 2024

ACS Appl. Nano Mater.

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This study showed the dual role of Nb (dopant and active site) in improving the structure−activity properties of shapecontrolled CeO 2 nanorods for the selective synthesis of functional imines and benzimidazoles via oxidative coupling of benzyl alcohols with anilines and o-phenylenediamines, respectively. The powder Xray diffraction (XRD) studies showed the lattice contraction of fluorite ceria due to the replacement of larger Ce 4+ (0.97 Å) by smaller Nb 5+ (0.74 Å) in the lattice, providing more defects (Ce 3+ and oxygen vacancies), as elucidated by XPS studies. The dispersion of Nb 2 O 5 on the surface of Nb-doped CeO 2 nanorods provided strong acid sites, as confirmed by pyridine-adsorbed Fourier transform infrared (FT-IR) study. The combined effect of oxygen vacancies and acid sites could promote the activation of molecular oxygen and benzyl alcohol, respectively, achieving ∼97−99% yields of imine and benzimidazole in the liquid-phase C−N coupling reactions over the Nb-CeO 2 nanorod catalyst calcined at 400 °C (NbCeNR4). The versatile catalytic efficiency of the NbCeNR4 nanomaterial is showcased by synthesizing various functional imines and benzimidazoles with good to excellent yields. The NbCeNR4 nanocatalyst is stable during the reaction as revealed by the hot filtration test and showed good catalytic reusability for 4 cycles. KEYWORDS: shape-controlled Nb 2 O 5 /Ce 1−x Nb x O 2−δ nanocatalyst, oxidative C−N cross-coupling, dual role of Nb, acid sites/oxygen vacancies, structure−activity correlation

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Structure–activity Correlation Of Shape-controlled Nb-ceo2 N...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nb₂O₅/Ce_1–xNb_xO_2−δ Nanorod Catalyst for Selective Oxidative Coupling of Aromatic Alcohols and Amines

Arun Kumar,

Kamali,

Putla

et al. 2024

ACS Appl. Nano Mater.

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Valorizing biomass waste glycerol to fuel additive at room temperature using a nanostructured WO3/Nb2O5 catalyst

Putla,

Subha,

Swapna

et al. 2024

Catalysis Communications

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Functionalized Metal-Free Carbon Nanosphere Catalyst for the Selective C–N Bond Formation under Open-Air Conditions

Krishan,

Swapna,

Chourasia

et al. 2024

ACS Omega

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A versatile shape-controlled carbon nanomaterial that can efficiently catalyze the selective C−N coupling reactions under metal-free and open-air conditions was developed by applying Ndoping and KOH activation strategies in candle soot (ANCS). The TEM and elemental mapping results showed the formation of sphereshaped carbon particles as well as the uniform distribution of nitrogen species in the carbon framework. KOH activation enhanced the specific surface area of carbon, whereas N-doping enriched the electron-deficient nature by introducing functional N-based pyrrolic/ graphitic structures in the carbon framework. The synergistic effect of N-doping and KOH activation significantly improved the catalytic efficiency of the carbon catalyst (ANCS), giving a 96% conversion of o-phenylenediamine (OPD) with a good selectivity to 2-phenylbenzimidazole (97%). In contrast, the pristine carbon exhibited very low activity (48% conversion of the OPD and 36% selectivity to 2-phenylbenzimidazole). Besides, the ANCS nanomaterial provided a facile catalytic approach for the homo-and cross-C−N condensation of various aromatic amines and diamines to produce diverse functional imines and benzimidazoles at mild conditions. This work provided promising insights into developing advanced, metal-free carbon-based catalysts for selective C−N coupling reactions to produce valuable drug motifs.

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One-pot synthesized efficient molybdenum‑niobium-oxide nanocatalyst for selective C-O and C-N coupling reactions at mild conditions

Cited by 4 publications

References 39 publications

Nb₂O₅/Ce_1–xNb_xO_2−δ Nanorod Catalyst for Selective Oxidative Coupling of Aromatic Alcohols and Amines

Nb₂O₅/Ce_1–xNb_xO_2−δ Nanorod Catalyst for Selective Oxidative Coupling of Aromatic Alcohols and Amines

Valorizing biomass waste glycerol to fuel additive at room temperature using a nanostructured WO3/Nb2O5 catalyst

Functionalized Metal-Free Carbon Nanosphere Catalyst for the Selective C–N Bond Formation under Open-Air Conditions

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One-pot synthesized efficient molybdenum‑niobium-oxide nanocatalyst for selective C-O and C-N coupling reactions at mild conditions

Cited by 4 publications

References 39 publications

Nb2O5/Ce1–xNbxO2−δ Nanorod Catalyst for Selective Oxidative Coupling of Aromatic Alcohols and Amines

Nb2O5/Ce1–xNbxO2−δ Nanorod Catalyst for Selective Oxidative Coupling of Aromatic Alcohols and Amines

Valorizing biomass waste glycerol to fuel additive at room temperature using a nanostructured WO3/Nb2O5 catalyst

Functionalized Metal-Free Carbon Nanosphere Catalyst for the Selective C–N Bond Formation under Open-Air Conditions

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Product

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Nb₂O₅/Ce_1–xNb_xO_2−δ Nanorod Catalyst for Selective Oxidative Coupling of Aromatic Alcohols and Amines

Nb₂O₅/Ce_1–xNb_xO_2−δ Nanorod Catalyst for Selective Oxidative Coupling of Aromatic Alcohols and Amines