Uniform single atomic Cu1-C4 sites anchored in graphdiyne for hydroxylation of benzene to phenol

Abstract

For single-atom catalysts (SACs), the catalyst supports are not only anchors for single atoms, but also modulators for geometric and electronic structures, which determine their catalytic performance. Selecting an appropriate support to prepare SACs with uniform coordination environments is critical for achieving optimal performance and clarifying the relationship between the structure and the property of SACs. Approaching such a goal is still a significant challenge. Taking advantage of the strong d-π interaction between Cu atoms and diacetylenic in Graphdiyne (GDY) support, we present an efficient and simple strategy for fabricating Cu single atoms anchored on GDY (Cu1/GDY) with uniform Cu1-C4 single sites under mild conditions. The Cu atomic structure was confirmed by combining synchrotron radiation X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and density functional theory (DFT) calculation. The as-prepared Cu1/GDY exhibits much higher activity than state-of-the-art SACs in direct benzene oxidation to phenol with H2O2 reaction, with turnover frequency values of 251 h−1 at room temperature and 1889 h−1 at 60°C, respectively. Furthermore, even with a high benzene conversion of 86%, high phenol selectivity (96%) is maintained, which can be ascribed to the hydrophobic and oleophyllic surface nature of Cu1/GDY for benzene adsorption and phenol desorption. Both experiments and DFT calculations indicate that Cu1-C4 single sites are more effective at activating H2O2 to form Cu = O bonds, which are important active intermediates for benzene oxidation to phenol.

Electronic Oxide–Support Strong Interactions in the Graphdiyne-Supported Cuprous Oxide Nanocluster Catalyst

“…However, traditional carbon materials (e.g., graphene, carbon nanotube) are rarely studied due to their inertness. Graphdiyne (GDY), as an emerging new type of carbon allotrope, is composed of the aromatic rings and carbon–carbon triple bonds (sp-hybridized carbon), rendering it high degree of π–π conjugate and electron transfer ability. − Especially, the unique alkyne-rich structure of GDY enables it as an ideal support for anchoring metals and oxides with strong d−π interactions, leading to charge transfer between them, which affects catalytic performance. − Therefore, GDY provides a promising support to study the electronic interactions beyond previously reported electronic metal–support interactions and electronic oxide/metal interactions. However, compared to numerous GDY-supported metal catalysts, limited attention was paid on GDY-supported oxide catalysts and none of them from the aspect of electronic oxide–support interactions.…”

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

“…[25][26][27] The strong interaction between metal atoms and carrier materials is very signicant for keeping the atomic dispersion of metal active centers and preventing agglomeration into particles. [28][29][30][31] Carbon materials have been proven to be ideal carrier materials because of their adjustable structure, excellent conductivity, stable physical and chemical properties. [32][33][34] The uniformly distributed defects on the surface of carbon materials also provide a basis for anchoring isolated active metal atoms.…”

Understanding the Density-Dependent Activity of Cu Single-Atom Catalyst in the Benzene Hydroxylation Reaction

“…The highest H 2 O 2 utilization efficiency was about 50% on 2.4-Cu 1 /NOC, which exhibited even better activity and significantly higher phenol selectivity than commercial TS-1 (Figure c). In comparison to previously reported metal SACs, the 2.4-Cu 1 /NOC sample also demonstrated much higher mass specific activity and H 2 O 2 utilization efficiency for the benzene oxidation reaction (Figure d). − ,− After 10 circles, there was no decline in benzene conversion or phenol selectivity (Figure S26), indicating excellent stability of 2.4-Cu 1 /NOC during the reaction. AC HAADF-STEM image and XAFS spectra showed that Cu atoms remained atomically dispersed and maintained the original coordination structure after reaction (Figures S27, S28).…”