Precisely Constructed Silver Active Sites in Gold Nanoclusters for Chemical Fixation of CO₂

Abstract

Precise control of the composition and structure of active sites in an atom‐by‐atom fashion remains insuperable for heterogeneous catalysts. Here, we introduce tailor‐made catalytic sites for the cycloaddition of CO2 to epoxides achieved by implementing Ag atoms at different levels of liberation in atomically precise Au nanoclusters. Our results reveal that a single open Ag site on the Au19Ag4 cluster improves the ring‐opening of epoxides and sequent CO2 insertion, while the partially exposed Ag site on the Au20Ag1 cluster exhibits a weak affinity for epoxides and poor efficiency for CO2 capture. Structural tunability imparted by the atom‐by‐atom tailoring and unusual atomic charges distributed on Au and Ag atoms of the three clusters seem to be crucial for promoting challenging bond cleavages and formations in the chemical utilization of CO2.

Physical Origin of Dual-Emission of Au–Ag Bimetallic Nanoclusters

“…Quantum-sized metal nanoclusters, which bridge the gap between organometallics and nanocrystals, exhibit dramatically unique electronic and optical properties, such as molecule-like energy gaps ( Schaaff et al, 1997 ; Lee et al, 2004 ; Negishi et al, 2005 ; Walter et al, 2008 ; Zhu et al, 2008 ; Russier-Antoine et al, 2014 ; Bertorelle et al, 2017 ; Chakraborty and Pradeep, 2017 ), intense photoluminescence ( Zheng et al, 2004 ; Zheng et al, 2007 ; Xie et al, 2009 ; Luo et al, 2012 ; Musnier et al, 2019 ) and catalytic properties ( Tsunoyama et al, 2009 ; Zhu et al, 2010 ; Li et al, 2016a ; Cai et al, 2019 ; Lv et al, 2019 ; Lv et al, 2020a ; Yang et al, 2020a ; Lv et al, 2020b ; Cai et al, 2020 ; Li et al, 2021 ). Luminescent thiolated-protected Au and Ag NCs in particular have attracted tremendous interest due to their wide applications in bio-imaging, bio-medicine, sensing, and catalysis ( Jin, 2010 ; Díez and Ras, 2011 ; Bonacic-Koutecky et al, 2012 ; Zheng et al, 2012 ; Luo et al, 2014 ; Sun and Jin, 2014 ; Jin et al, 2016 ; Lei et al, 2018 ; Yan et al, 2018 ; Ungor et al, 2021 ).…”

Reactivity and Recyclability of Ligand‐Protected Metal Cluster Catalysts for CO2 Transformation

“…In contrary, slight shifts of BEs appeared to be Ag valence state (Figure 4b). Compared to Ag 28 Au 1 , the Ag 3d 5/2 profiles of Cu 12 Ag 17 and Cu 12 Ag 16 Au 1 showed slightly higher BEs, indicating that the Ag charge state of CuAg clusters was more negative [30, 33] . For Cu charge state, as showed in Figure 4c, unlike CuCl 2 XPS spectra, the doublet Cu 2p XPS profiles of Cu 12 Ag 17 and Cu 12 Ag 16 Au 1 were considerably shifted to lower BEs compared to Cu 2+ case, implying that Cu atoms of CuAg clusters were less than bivalent.…”

“…Compared to convoluted behaviors between surface and inside atoms of conventional heterogeneous catalysts, the clusters provide possible to study only one factor contribution to overall performances using unique pairs of clusters that possess the same surface with different cores or the same core with different surfaces [26, 27] . On the other hand, ligand‐protected metal clusters have been explored as homogeneous catalysts, where they keep advantages such as defined metal centre for creating reactive sites and surface ligands for orienting reactants and controlling selectivity, as well as overcome such minuses as separation from reaction systems and further boost their reutilization [28–30] . Obviously, these metal clusters provide opportunities to solve intrinsic issues related to homogeneous and heterogeneous catalysis.…”

Vacancy-cluster-mediated surface activation for boosting CO2 chemical fixation

“…To gain in-depth understanding on the effects of Fe-Cl vacancy cluster in cycloaddition of CO 2 with epoxides, in-situ diffuse reflectance infrared Fourier-transform spectroscopy (insitu DRIFTS) measurements were carried out, 40 where the catalyst and PO were mixed in a reaction chamber under 0.3-MPa CO 2 atmosphere at 413 K. According to Figure S19, the ring-opening of PO is evidenced by gradually increasing of the peak around ~670 cm -1 that could be assigned to the formation of C-Cl bond. [41][42][43] Such a feature clearly confirms that Cl atom at Fe-Cl vacancy cluster could serve as an electron-donor unit for attacking the electrophilic carbon atom of PO.…”