Single-Atom Mn Active Site in a Triol-Stabilized β-Anderson Manganohexamolybdate for Enhanced Catalytic Activity towards Adipic Acid Production

Abstract

Adipic acid is an important raw chemical for the commercial production of polyamides and polyesters. The traditional industrial adipic acid production utilizes nitric acid to oxidize KA oil (mixtures of cyclohexanone and cyclohexanol), leading to the emission of N 2 O and thus causing ozone depletion, global warming, and acid rain. Herein, we reported an organically functionalized β-isomer of Anderson polyoxometalates (POMs) nanocluster with single-atom Mn, β-{[H 3 NC(CH 2 O) 3 ] 2 MnMo 6 O 18 } − (1), as a highly active catalyst to selectively catalyze the oxidation of cyclohexanone, cyclohexanol, or KA oil with atom economy use of 30% H 2 O 2 for the eco-friendly synthesis of adipic acid. The catalyst has been characterized by single crystal and powder XRD, XPS, ESI-MS, FT-IR, and NMR. A cyclohexanone (cyclohexanol) conversion of >99.9% with an adipic acid selectivity of~97.1% (~85.3%) could be achieved over catalyst 1 with high turnover frequency of 2427.5 h −1 (2132.5 h −1). It has been demonstrated that the existence of Mn 3+ atom active site in catalyst 1 and the special butterfly-shaped topology of POMs both play vital roles in the enhancement of catalytic activity.

Recent advances of polyoxometalate-catalyzed selective oxidation based on structural classification

“…Among them, the Cu-containing POM exhibited the highest yield (Table 7), as well as good durability and recyclability. Due to the strong electron-withdrawing abilities of the MoO 6 groups, the planar arrangement of the six Mo VI centres around the central heterometal can greatly enhance the Lewis (Luo et al, 2018). A comparison with the precursor or analogue implied that both the existence of a single Mn 3+ active site in the catalyst and the special butterfly-shaped topology of the POM were vital to activity (Table 8).…”

Recent Progress in Adipic Acid Synthesis Over Heterogeneous Catalysts

“…Cyclohexane, cyclohexanol, cyclohexanone can be oxidized to produce AA without formation of any greenhouse gases (Sato et al, 1998;Chatterjee et al, 2018;Luo et al, 2018;Mazzi et al, 2018;Mouheb et al, 2018;Wang et al, 2018). Oxygen, air, hydrogen peroxide (H 2 O 2 ) are regarded as clean oxidant since they give water as the only byproduct.…”

Ag10Ti28‐Oxo Cluster Containing Single‐Atom Silver Sites: Atomic Structure and Synergistic Electronic Properties

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Supported single-atom catalysts have been emerging as promising materials in av ariety of energy catalysis applications.H owever,s tudying the role of metal-support interactions at the molecular level remains am ajor challenge, primarily due to the lacko fp recise atomic structures.I nt his work, by replacing the frequently used TiO 2 support with its molecular analogue,t itanium-oxo cluster (TOC), we successfully produced anew kind of Ti-O material doped with single silver sites.T he as-obtained Ag 10 Ti 28 cluster,c ontaining four exposed and six embedded Ag sites,isthe largest noble-metaldoped Ti-O cluster reported to date.Density functional theory (DFT) calculations show that the Ag 10 Ti 28 core exhibits properties distinct from those of metallic Ag-based materials. [7][8][9][10][11] However,the preparation of single-atom-distributed catalysts is still quite challenging,a nd their characterization is highly dependent on advanced microscopy and synchrotron radiation techniques. These results prove that the synergism of active surface metal atoms and the Ti-O cluster support result in unique physical properties,w hich might open anew direction for single-atom-included catalysts.

Inthe field of catalysis,i th as been well established that the catalytic performance of materials is highly dependent on size,m orphology,a nd structure.

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“…[1][2][3][4][5][6] Especially,t he recently developed single-atom catalysts are attracting tremendous interest due to their excellent activity and selectivity. [7][8][9][10][11] However,the preparation of single-atom-distributed catalysts is still quite challenging,a nd their characterization is highly dependent on advanced microscopy and synchrotron radiation techniques. [12,13] Moreover,d ue to the lack of atomic structures,i ti sr ather difficult to study the metal-support interaction and the functional role of the support which is crucial for the performance of such catalyst systems.…”