Atomically Defined Undercoordinated Copper Active Sites over Nitrogen‐Doped Carbon for Aerobic Oxidation of Alcohols

Abstract

Lee et al. reported a series of highly active single-site mesoporous Pd/Al 2 O 3 catalysts for selective aerobic oxidation of allylic alcohols. [9] Grassi et al. described gold nanoparticles enclosed in a polymer matrix for oxidative esterification of cinnamyl alcohol with alkyl alcohols. [10] Lee and co-workers developed a zirconia-supported ruthenium catalyst for efficient aerobic oxidation of alcohols to aldehydes. [11] Li et al. found that metal/oxide supported catalysts, such as FeO/Pt(111) or Cu 2 O/ Ag(111) exhibit interfacial effects that significantly improve the efficacy in the selective oxidation of primary alcohols. [4] These nanoparticle-based catalysts, though effective in mediating selective oxidation reactions, have significant drawbacks of high cost, low selectivity, and rapid deactivation in harsh conditions. As such, the development of more practical and economical catalyst systems has been a major challenge in both industrial and academic areas.In 2011, Zhang and co-workers, for the first time, presented a comprehensive study and coined the concept of single-atom catalysis. [12] As a new frontier, single atom catalysts (SACs) have gained wide attention because of their great advantages of high atom efficiency and unique catalytic activity. [13][14][15][16][17][18][19][20] SACs possess distinctive chemical and physical properties and a unique coordination environment that is different from their nanoparticle counterparts. [21][22][23][24][25] Moreover, SACs have been found to be effective in bridging homogeneous and heterogeneous catalysis. [26][27][28][29] Selective aerobic oxidation of alcohols offers an attractive means to address challenges in the modern chemical industry, but the development of nonnoble metal catalysts with superior efficacy for this reaction remains a grand challenge. Here, this study reports on such a catalyst based on atomically defined undercoordinated copper atoms over nitrogen-doped carbon support as an efficient, durable, and scalable heterogeneous catalyst for selective aerobic oxidation of alcohols. This catalyst exhibits extremely high intrinsic catalytic activity (TOF of 7692 h −1 ) in the oxidation of cinnamyl alcohol to afford cinnamaldehyde, along with exceptional recyclability (at least eight cycles), scalability, and broad substrate scope. DFT calculations suggest that the high activity derives from the low oxidation state and the unique co ordination environment of the copper sites in the catalyst. These findings pave the way for the design of highly active and stable single atom catalysts to potentially address challenges in synthetic chemistry.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.202106614.

A high-efficiency zirconium-based single-atom catalyst for the transformation of biomass-derived 5 hydroxymethylfurfural to 2,5-bis(hydroxymethyl)furan with nearly 100% selectivity

“…80 Additionally, compared with NC, the reducing role of Zr in the pyrolysis process increased the specific surface area (614 m 2 g −1 ), pore size (5.8 nm) and pore volume (0.716 cm 3 g −1 ) of Zr/NC (Table S1 †), which could significantly facilitate the exposure of active sites and the diffusion of reaction species, and then contribute to the catalytic process. 81 From the scanning electron microscopy (SEM) images in Fig. 2A and B, it can be seen that ZIF-8 and Zr@ZIF-8 displayed a similar rhombic dodecahedron shape with a smooth surface, further indicating that Zr doping did not affect the main structure of ZIF-8, which was in accordance with the results of XRD and FT-IR in Fig.…”

“…80 Additionally, compared with NC, the reducing role of Zr in the pyrolysis process increased the specific surface area (614 m 2 g −1 ), pore size (5.8 nm) and pore volume (0.716 cm 3 g −1 ) of Zr/NC (Table S1†), which could significantly facilitate the exposure of active sites and the diffusion of reaction species, and then contribute to the catalytic process. 81…”

Rational design, application and dynamic evolution of Cu–N–C single-atom catalysts

“…Li et al prepared a Cu 1 /N-C catalyst for the oxidation of cinnamyl alcohol and found that the superoxide produced aer O 2 activation can be combined with cinnamyl alcohol to produce cinnamaldehyde. 168 The Cu dorbital and O p-orbital for cinnamyl alcohol adsorption on Cu 1 / N-C overlapped near −1.30 eV, which is conducive to the catalytic reaction. In organic oxidation reactions, conversion and selectivity are the key parameters to consider the performance of catalysts.…”

Enhancing Heterogeneous Catalysis by Electronic Property Regulation of Single Atom Catalysts

“…Recently, non-precious SACs were prepared to selectively catalyze the oxidation of alcohols in the face of high cost and scarcity of precious metals 49,50,112,[119][120][121] . The replacement of noble metal is significantly important in cutting cost in industrial application, which requires intensive research toward non-noble metal based SACs.…”

“…The M-dN type was widely studied owing to its relatively simple and uniform active sites while an enormous gap is left in the other two types attributed to their complicated electronic states of active sites, which leads to difficulty in characterization and calculation. The nitride-doped carbon (CN) is extensively selected as supports for M-dN [48][49][50][51][52][53][54] . However, new doped sites like O, P, S, Cl have also been reported [55][56][57][58][59][60][61] .…”