Understanding the decomposition process of the Pt₁Ag₂₄(SPhCl₂)₁₈ nanocluster at the atomic level

Abstract

We report the decomposition of the Pt₁Ag₂₄(SPhCl₂)₁₈ nanocluster into a crown-like Pt₁Ag₄(SR)₈ (SR = 2,4-SPhCl₂ and 4-SPhBr) complex. UV-vis spectra and single crystal X-ray diffraction were used to track the structure-conversion process. Based on the total structure, the differences in ligand exchange rates at different sites and the effects on the stability were mapped out. This work can not only help us understand the ligand exchange behavior of the clusters, but also provide experimental support for the design of stable metal clusters.

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1 Introduction

Atomically precise metal nanoclusters can help elucidate the precise relationship between structure and properties,^1–15 which is crucial to comprehend the nanocluster stability,^16–19 transformation mechanism and growth mechanism in solution.^20–25 The interaction between clusters not only can help us understand the interaction of nanoparticles at the atomic level,^26,27 but also aids in designing and synthesizing clusters of specific sizes or characteristics.^28–32 Indeed, based on the ligand-exchange-induced size/structure transformation (LEIST) method, a series of clusters with monodispersity have been synthesized and their structures determined by Single crystal X-ray diffraction (SC-XRD).^33–40 It is worth noting that there are two major behaviours in LEIST: (i) conversion. For instance, the size transformation of the Au₃₈(SC₂H₄Ph)₂₄ nanocluster to the Au₃₆(SPh^tBu)₂₄ nanocluster induced by HSPh^tBu ligands.³³ More importantly, due to the precise structure, the mechanism of such a process can be studied at the atomic level; (ii) decomposition. In the LESIT method, partial or complete decomposition usually occurs.^22,41,42 For example, the synthesis of the monodisperse Pt₁Au₂₄(SC₂H₄Ph)₁₈ nanocluster is accompanied by the decomposition of the Au₂₅(SC₂H₄Ph)₁₈ nanocluster.⁴¹ In past research, the process and mechanism of cluster size transformation in LESIT have been extensively studied.^33,43–46 However, understanding the decomposition process of nanoclusters at the atomic level is crucial for us to understand the origin of stability, but there are few studies.

Herein, we monitored the decomposition of Pt₁Ag₂₄(SPhCl₂)₁₈ nanoclusters with UV-vis spectra and SC-XRD.⁴⁷ We obtained three crystals, including two intermediates (Pt₁Ag₂₄(SPhCl₂)_7.51(SPh^tBr)_12.49, denoted as NC-I; Pt₁Ag₂₄(SPhCl₂)_2.28(SPh^tBr)_17.72, denoted as NC-II) and one decomposed product (Pt₁Ag₄(SPhCl₂)_4.31(SPh^tBr)_3.69, denoted as Pt₁Ag₄).⁴⁵ Through the structural analysis of these crystals and calculating the occupancy ratio of exchanged ligands, the ligand exchange rate at different positions on the clusters has been mapped out.⁴⁸ It is worth noting that, although some ligands are located at symmetrical positions on the C₃ axis, the ligand exchange rates show significant differences. These subtle differences lead to the decomposition of the cluster.

2 Experimental methods

2.1 Chemicals

All reagents were purchased from XiLong Scientific and used directly without further purification. Silver nitrate (AgNO₃, 99%, metal basis), potassium tetrachloroplatinate (II) (K₂PtCl₄; 99%, metal basis), 2,4-dichlorobenzenethiol (HSPh^2,4Cl₂, 99%), 4-bromothiophenol (HSPh^tBr, 99%), tetraphenylphosphonium bromide (PPh₄Br, 98%), sodium borohydride (NaBH₄, 98%), triethylamine (C₆H₁₅N, 99.5%), dichloromethane (CH₂Cl₂, HPLC), methanol (CH₃OH, HPLC), N,N-dimethylformamide (DMF, HPLC), hexane (C₆H₁₄, HPLC), and diethyl ether ((CH₃CH₂)₂O, HPLC) were used.

2.2 Synthesis of Pt₁Ag₂₄(SPhCl₂)₁₈ nanocluster

The sample of Pt₁Ag₂₄(SPhCl₂)₁₈ was synthesized based on the previously reported process with minor modifications.⁴⁷ Firstly, AgNO₃ (10 mg, 0.0588 mmol) was dissolved in CH₃OH. CH₂Cl₂ and K₂PtCl₄ (10 mg, 0.0240 mmol) were then added to the solution to form a pale-yellow mixture. In an ice bath, the mixture was cooled to 0 °C. Then, 2,4-dichlorobenzenethiol (10 μL, 0.0791 mmol) and tetraphenylphosphonium bromide (10 mg, 0.0238 mmol) were added in turn. After 30 min, 1 mL NaBH₄ aqueous solution (40 mg mL⁻¹, 1.057 mmol) and triethylamine (50 μL, 0.358 mmol) were added quickly to the mixture under vigorous stirring. This reaction was further aged for 12 h at 0 °C. Whereafter, the aqueous phase was removed. The mixture in the organic phase was washed three times with (CH₃CH₂)₂O (2 × 10 mL). After a week, dark-red crystals were acquired in CH₂Cl₂/hexane at room temperature.

2.3 Conversion from Pt₁Ag₂₄(SPhCl₂)₁₈ to Pt₁Ag₄(SR)₈

Briefly, Pt₁Ag₂₄(SPhCl₂)₁₈ (10 mg, 0.00167 mmol) crystals were dissolved in 5 mL DMF, then HSPh^tBr was added in different molar ratios. The progress of the reaction is less dependent on the time, and is highly dependent on the molar ratio of HSPh^tBr mercaptan ligand added. After the addition of 200 equivalents of HSPh^tBr, all Pt₁Ag₂₄(SPhCl₂)₁₈ nanoclusters were converted to Pt₁Ag₄(SR)₈ complexes. The crude products of Pt₁Ag₄(SR)₈ were washed two times with (CH₃CH₂)₂O (2 × 10 mL). Single crystal growth of Pt₁Ag₂₄(SR)₂₀ and Pt₁Ag₄(SR)₈ was accomplished by vapor diffusion of (CH₃CH₂)₂O into a concentrated solution of the Pt₁Ag₄(SR)₈ in CH₂Cl₂ for 2 days.

2.4 Synthesis of NC-I and NC-II

In the process of transforming Pt₁Ag₂₄(SPhCl₂)₁₈ to Pt₁Ag₄(SR)₈, the reaction was halted at a distinctive juncture. For NC-I, after 60 equivalents of HSPh^tBr was added and followed by stirring 3 minutes, the reaction was terminated. For NC-II, after 100 equivalents of HSPh^tBr was added and followed by stirring for 3 minutes, the reaction was terminated. The crude products of NC-I and NC-II were washed two times with (CH₃CH₂)₂O (2 × 10 mL). Single crystal growth of NC-I and NC-II was accomplished through vapor diffusion of (CH₃CH₂)₂O into a concentrated solution of the NC-I and NC-II in CH₂Cl₂ for 2 days.

2.5 Characterization

All UV-vis absorption spectra of the structure conversion process were acquired on UV-1810 at room temperature. The data collections for single crystal X-ray diffraction were carried out on a STOE stadivari diffractometer. Data reductions and absorption corrections were performed using the X-Area. The structure was solved by intrinsic phasing and refined with full-matrix least squares on F² using the SHELXTL software package. All non-hydrogen atoms were refined anisotropically, and all the hydrogen atoms were set in geometrically calculated positions and refined isotopically using a riding model. In order to confirm the ligand type of the cluster, the Br position was refined as free variables.

3 Results and discussion

3.1 Monitoring the transformation process from Pt₁Ag₂₄(SPhCl₂)₁₈ to Pt₁Ag₄(SR)₈

In this work, our focus centered on the decomposition of metal nanoclusters, and we selected Pt₁Ag₂₄(SPhCl₂)₁₈ (where, SPhCl₂ = 2,4-dichlorothiolated) nanocluster as the model due to its metastability in the presence of aryl mercaptan.^45,49–51 As shown in Fig. 1, the UV-vis absorption spectrum of Pt₁Ag₂₄(SPhCl₂)₁₈ nanocluster exhibits two characteristic absorption peaks at 455 nm and 570 nm, with a shoulder at 400 nm, consistent with the reported result.⁴⁷ Pt₁Ag₂₄(SPhCl₂)₁₈ nanocluster was converted into Pt₁Ag₂₄(SR)₂₀ (where SR is the mixture of 2,4-SPhCl₂ and 4-SPhBr) nanocluster after adding less than 60 equivalents of 4-bromothiophenol ligand (HSPh^tBr), which is similar to the reported results.⁴⁵ Where characteristic absorptions of Pt₁Ag₂₄(SR)₂₀ (at 400 nm, 435 nm, 480 nm, and 575 nm) became prominent, while those of Pt₁Ag₂₄(SPhCl₂)₁₈ (455 nm, 570 nm and 400 nm) diminished. In this series of spectra, four isosbestic points were discovered at 400, 420, 480, and 505 nm, signifying the process is quantitative. Simultaneously, the colour of the solution turned from atrovirens to reddish orange (Fig. S1†). The reason for the transformation from Pt₁Ag₂₄(SPhCl₂)₁₈ to Pt₁Ag₂₄(SR)₂₀ is that three Ag₂(SR)₃ staple motifs of Pt₁Ag₂₄(SPhCl₂)₁₈ are aggregated to be one Ag₆(SR)₁₀ surface caps at nanocluster poles by the addition and induction of free thiol ligands. After adding 60 equivalents of 4-bromothiophenol ligand, the absorbance of the sample decreases as the amount of ligand increases. The constant peak position and the ratio of the different peaks indicate the clusters have been gradually decomposed into complexes. After adding 200 equivalents of HSPh^tBr to the solution, there is no peak after 400 nm, indicating that the nanoclusters are completely decomposed into metal complexes. Concurrently, the colour of the solution turned from reddish orange to pale yellow (Fig. S1†).

Fig. 1 The UV-vis absorption spectra of transformation process from Pt₁Ag₂₄(SPhCl₂)₁₈ nanocluster to Pt₁Ag₄(SR)₈ complex. The UV-vis absorption spectra with diverse ratios of HSPh^tBr mercaptan ligand to Pt₁Ag₂₄(SPhCl₂)₁₈ nanocluster; (eq. represents the molar ratio of HSPh^tBr mercaptan to Pt₁Ag₂₄(SPhCl₂)₁₈ nanocluster).

3.2 Crystal structure of Pt₁Ag₂₄(SR)₂₀ and Pt₁Ag₄(SR)₈

To elucidate the detailed decomposition process of this nanocluster, the reaction was stopped at the specific molar ratios.⁵² As shown in Fig. 1 (solid line), the crystal of Pt₁Ag₂₄(SPhCl₂)_7.51(SPh^tBr)_12.49 (magenta line, NC-I), Pt₁Ag₂₄(SPhCl₂)_2.28(SPh^tBr)_17.72 (red line, NC-II) and Pt₁Ag₄(SPhCl₂)_4.31(SPh^tBr)_3.69 (orange line, Pt₁Ag₄(SR)₈) were obtained (Fig. S2†). SC-XRD was used to determine the overall structure of these crystals, respectively (Fig. S3†). Additionally, UV-vis spectra of NC-I, NC-II, and Pt₁Ag₄ crystals are shown in Fig. S4 and S5.† Results revealed that NC-I exhibits two strong absorption peaks at 400 nm and 482 nm, with two weaker peaks at 435 nm and 575 nm (Fig. S4†). Similarly, NC-II also showed two main absorption peaks (397 nm and 480 nm) and two weaker peaks (432 nm and 564 nm). Compared to NC-I, a blue shift was observed in the UV-vis spectrum of NC-II, attributed to different occupancy ratios of ligands. Pt₁Ag₄ composite only displayed a faint peak at 442 nm (Fig. S5†).

The crystal structure analysis of Pt₁Ag₂₄(SR)₂₀ and Pt₁Ag₄(SR)₈ is presented in Fig. 2. For the Pt₁Ag₂₄(SR)₂₀ nanocluster, the entire Pt₁Ag₂₄(SR)₂₀ structure exhibits an icosahedral Pt₁Ag₁₂ metal kernel protected by two Ag₆(SR)₁₀ staple motifs (Fig. 2a–c).⁴⁵ Consequently, the overall framework of Pt₁Ag₂₄(SR)₂₀ can be regarded as “Pt₁Ag₁₂ + 2*Ag₆(SR)₁₀”. Each Ag₆(SR)₁₀ motif comprises three irregular hexagons (Fig. 2a), where three irregular hexagons are fused together by sharing the Ag–SR–Ag edges and terminated with three SR ligands. In the Pt₁Ag₄(SR)₈ complex (Fig. 2d–f), the Pt atom exists independently of the Ag₄ plane, with an average distance of 3.4 Å. Among the eight bridging thiolates, four bridging thiolates are bonded to Pt and Ag atoms, while the others link between two Ag atoms. Alternatively, the structure of Pt₁Ag₄(SR)₈ can be viewed as two layers: the upper layer (A layer) resembles “a cross” with Pt₁(SR)₄, and the lower layer (B layer) is Ag₄(SR)₄, akin to “a plate”. Notably, the entire structure of Pt₁Ag₄(SR)₈ exhibits C₄ Axial Symmetry (Fig. 2d). The Ag–Ag bonds in the Pt₁Ag₄ kernel range from 3.067 to 3.165 Å (average: 3.115 Å), surpassing the Ag–Ag bond distance (2.889 Å) in bulk silver. Additionally, the Pt–S bonds range from 2.327 to 2.334 Å (average: 2.331 Å). There are two kinds of bridging thiolates in Pt₁Ag₄(SR)₈ complex,⁵³ with average Pt–S–Ag angle of 87.64 to 89.03° (average: 88.33°) and Ag–S–Ag angle of 77.22 to 79.63° (average: 78.26°). The clockwise and anticlockwise of the thiol ligands reveal the Pt₁Ag₄(SR)₈ complex is racemic (Fig. 2f and S6†).²⁵

Fig. 2 Structural anatomy of Pt₁Ag₂₄(SR)₂₀ and Pt₁Ag₄(SR)₈. (a) Two Ag₆(SR)₁₀ staple motifs of Pt₁Ag₂₄(SR)₂₀; (b) the Pt₁Ag₁₂ kernel of Pt₁Ag₂₄(SR)₂₀; (c) X-ray structure of the Pt₁Ag₂₄(SR)₂₀; (d) X-ray structure of the Pt₁Ag₄(SR)₈; (e) top view of the Pt₁Ag₄(SR)₈ framework; (f) top view of the overall structure of Pt₁Ag₄(SR)₈. Color labels: bright green = Pt; pink = Ag; yellow = S; grey = C. H, Cl, Br atoms and some carbon atoms are omitted for clarity.

Building upon the aforementioned results, the transformation from Pt₁Ag₂₄(SPhCl₂)₁₈ to Pt₁Ag₄(SR)₈ can be classified into two stages. A comprehensive diagram of the entire transformation process is depicted in Fig. 3. According to the symmetry of the crystal, only half of the Ag₂(SR)₃ motif for Pt₁Ag₂₄(SR)₁₈ and the Ag₆(SR)₁₀ motif for Pt₁Ag₂₄(SR)₂₀ are shown in Fig. 3 for clarity. To better illustrate the variation in ligand occupancy ratio and species during the conversion process, S atoms were used as substitutes for the entire mercaptan ligands. And all ligands were divided into three categories: ligands completely occupied by 2,4-SPhCl₂ were highlighted in yellow, ligands absolutely occupied by 4-SPhBr were represented by red atoms and ligands occupied by both 2,4-SPhCl₂ and 4-SPhBr were highlighted in turquois.

Fig. 3 Transformation pathway from Pt₁Ag₂₄(SR)₁₈ to Pt₁Ag₄(SR)₈. (a) Partial structure of the Pt₁Ag₂₄(SPhCl₂)₁₈: Pt₁Ag₁₂ core + 3*Ag₂(SR)₃ motifs; (b) partial structure of the NC-I: Pt₁Ag₁₂ core + Ag₆(SR)₁₀ top unit; (c) partial structure of the NC-II: Pt₁Ag₁₂ core + Ag₆(SR)₁₀ top unit; (d) and (e) overall structure of the Pt₁Ag₄(SR)₈. Color labels: bright green = Pt; pink = Ag; yellow = 2,4-SPhCl₂; red = 4-SPhBr; turquois = 2,4-SPhCl₂/4-SPhBr; H, C, Cl and Br atoms are omitted for clarity.

Stage 1: In the first stage (from 0 eq. to 60 eq.), Pt₁Ag₂₄(SPhCl₂)₁₈ was converted to Pt₁Ag₂₄(SPhCl₂)_7.51(SPh^tBr)_12.49 (NC-I), matching the UV-vis spectra from 0 eq. to 60 eq. (Fig. 1) and the transformation process from Pt₁Ag₂₄(SPhCl₂)₁₈ (Fig. 3a) to NC-I (Fig. 3b). The average number of 2,4-SPhCl₂ reached ca. 7.51 in NC-I. Stage 2: In the second stage (from 60 eq. to 200 eq.), as shown in Fig. 3b–e, Pt₁Ag₂₄(SPhCl₂)_7.51(SPh^tBr)_12.49 (NC-I) was decomposed into Pt₁Ag₄(SR)₈ or exchanged by the HSPh^tBr ligand into Pt₁Ag₂₄(SPhCl₂)_2.28(SPh^tBr)_17.72 (NC-II) with the addition of HSPh^tBr mercaptan. The average number of 2,4-SPhCl₂ in NC-II reached a maximum of approximately 2.28. Further, NC-II was also decomposed into Pt₁Ag₄(SR)₈. Detailed crystal parameters were provided in Tables S1–S3.† Additionally, the disparate occupancy ratios of ligands within NC-I and NC-II nanoclusters result in their respective crystallization in distinct crystal systems—triclinic and monoclinic systems (Fig. S7†). Furthermore, this further impacts the arrangement of cluster molecules, as although the cluster molecules of NC-I and NC-II are arranged in an “ABAB” pattern, the orientation of the molecules' arrangement is entirely different (Fig. S8†).^15,54

3.3 The conversion mechanism from Pt₁Ag₂₄(SR)₁₈ to Pt₁Ag₄(SR)₈

As illustrated in Fig. 3, both NC-I and NC-II nanoclusters show similar structures. The variance in the occupancy ratio of 2,4-SPhCl₂ and 4-SPhBr ligands reveals the ligand exchange process of nanoclusters (Table S4†). Notably, NC-I and NC-II, along with Pt₁Ag₄, were examined for the occupancy ratios (x%) of 2,4-SPhCl₂ in mercaptan ligands, as depicted in Fig. 4.^45,55,56 To enhance clarity, we categorized ten mercaptan ligands into four types in NC-I and NC-II: type I (ligand-1, ligand-2, and ligand-3), type II (ligand-4, ligand-5, and ligand-6), type III (ligand-7, ligand-8, and ligand-9), and type IV (ligand-10).

Fig. 4 The corresponding occupancy ratios of 2,4-SPhCl₂ unit in NC-I, NC-II and Pt₁Ag₄. (a) Partial structure of the NC-I (Pt₁Ag₁₂ kernel + Ag₆(SR)₁₀ top unit) was displayed to explain the type of ligand. (b) Partial structure of the NC-II (Pt₁Ag₁₂ core + Ag₆(SR)₁₀ top unit) was displayed to explain the type of ligand. (c) The structure of the Pt₁Ag₄ was displayed. The occupancy ratios of 2,4-SPhCl₂ unit were displayed in (x%). Color labels: bright green = Pt; pink = Ag; red = 4-SPhBr; turquois = 2,4-SPhCl₂ and 4-SPhBr. H, C, Cl and Br atoms are omitted for clarity. Notably, the occupancy ratios of NC-I are the average occupancy ratios among the three cluster molecules in single crystal.

The occupancy ratios of 2,4-SPhCl₂ and 4-SPhBr units in NC-I, NC-II, and Pt₁Ag₄ were summarized in Table S4,† and detailed information about related bonds is shown in Table S5.† Obviously, the exchange sites of type III (ligand-7, ligand-8 and ligand-9) were completely exchanged by 4-SPhBr ligands in NC-I (Fig. 4a), indicating that thiol ligands in type III are more susceptible to be exchanged. Similarly, the occupancy ratio of 2,4-SPhCl₂ to type IV (ligand-10) is only 10% in NC-I (Fig. 4a), and is fully exchanged by 4-SPhBr in NC-II (Fig. 4b). The occupancy ratios of 2,4-SPhCl₂ at these four ligand sites in NC-I and NC-II suggest that they are not critical for the decomposition of the Pt₁Ag₂₄(SR)₂₀ nanocluster. For the ligands of type I, the occupancy ratio of 2,4-SPhCl₂ to ligand-1 in NC-I was 50%, decreasing to 14% in NC-II. Concurrently, the ratio of ligand-2 and ligand-3 also decreased. Fig. 4 and Table S4† showed the following ratio of ligand-2: NC-I/NC-II = 42%/24%, and ligand-3: NC-I/NC-II = 79%/25%. Regarding the ligands of type II, at these positions, the occupancy ratios of 2,4-SPhCl₂ in these three ligands significantly decrease from NC-I to NC-II (Fig. 4a, b and Table S4†). Specifically, in NC-I and NC-II, the occupancy ratios of 2,4-SPhCl₂ in ligand-4 are 71.6% and 0% (Fig. 4a, b and Table S4†), respectively, indicating that 2,4-SPhCl₂ units were fully exchanged by 4-SPhBr in NC-II. Fig. 4 and Table S4† showed the following occupancy ratios of 2,4-SPhCl₂ in the ligands of type II, ligand-5: NC-I/NC-II = 60.7%/22% and ligand-6: NC-I/NC-II = 62.3%/29%, respectively. However, the relevant S–Ag bond lengths in NC-I and NC-II did not change significantly (Table S5†).

According to the analysis of the occupancy ratios of 2,4-SPhCl₂ in the ten ligands, we found that four ligands of type III and type IV were independent of the decomposition of Pt₁Ag₂₄(SR)₂₀. Additionally, due to the significantly higher occupancy ratios of 2,4-SPhCl₂ in Pt₁Ag₄ compared to NC-II (Fig. 4b, c and Table S4†), and considering the abundant presence of HSPh^tBr thiol ligands in the solution, it is impossible that the 2,4-SPhCl₂ and 4-SPhBr units in Pt₁Ag₄ to originate from NC-II. Furthermore, for the six mercaptan ligands of type I and type II, the average occupancy ratio of the 2,4-SPhCl₂ unit in NC-I (average: 0.609) is similar to the average occupancy ratio of 2,4-SPhCl₂ in Pt₁Ag₄(SR)₈ (average: 0.539) in Fig. 4a, c and Table S4.† Based on existing technology, it is difficult to directly observe the transfer process of a single ligand/metal in the nanocluster transformation process. It is reasonable to assume that the most likely reason for the similar ratio is that the ligands on the Pt₁Ag₄(SR)₈ complex are inherited from the ligands of type I and type II in NC-I. We proposed the possible decomposition mechanism of the Pt₁Ag₂₄(SR)₁₈ nanocluster (Fig. 5). One Pt atom, four Ag atoms and eight mercaptan ligands containing 2,4-SPhCl₂ and 4-SPhBr units formed Pt₁Ag₄(SR)₈. And one central Pt atom, twelve thiol ligands of type I and type II, and sixteen Ag atoms connected to twelve thiol ligands in NC-I are potential sources of one Pt atom, eight thiol ligands and four silver atoms in Pt₁Ag₄.

Fig. 5 The possible decomposition mechanism from NC-I nanocluster to Pt₁Ag₄(SR)₈ complex. Color labels: bright green = Pt; pink = Ag; red = 4-SPhBr; turquois = 2,4-SPhCl₂ and 4-SPhBr. H, C, Cl and Br atoms are omitted for clarity.

4 Conclusions

In summary, we have presented a study on the decomposition of Pt₁Ag₂₄(SPhCl₂)₁₈ nanocluster leading to the formation of the Pt₁Ag₄(SR)₈ complex. This process was monitored using UV-vis spectra and SC-XRD. The pathway of transformation can be roughly divided into two stages: (I) HSPh^tBr-triggered size transformation of Pt₁Ag₂₄(SPhCl₂)₁₈ forms NC-I; (II) structural decomposition of NC-I to Pt₁Ag₄(SR)₈ and ligand exchange of NC-I to NC-II. And Pt₁Ag₄(SR)₈ complex is inherited from the Pt atom, partial Ag atoms, and the ligand containing 2,4-SPhCl₂ and 4-SPhBr in NC-I.

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

We acknowledge the financial support provided by the National Natural Science Foundation of China (21803001 and 21771156) and Start-up Funding from Qingdao University of Science and Technology.

Notes and references

1. B. Bhattarai, Y. Zaker, A. Atnagulov, B. Yoon, U. Landman and T. P. Bigioni, Acc. Chem. Res., 2018, 51, 3104–3113.
2. A. W. Cook and T. W. Hayton, Acc. Chem. Res., 2018, 51, 2456–2464.
3. K. Konishi, M. Iwasaki and Y. Shichibu, Acc. Chem. Res., 2018, 51, 3125–3133.
4. Z. Lei, X. K. Wan, S. F. Yuan, Z. J. Guan and Q. M. Wang, Acc. Chem. Res., 2018, 51, 2465–2474.
5. R. L. Whetten, H. C. Weissker, J. J. Pelayo, S. M. Mullins, X. Lopez-Lozano and I. L. Garzon, Acc. Chem. Res., 2019, 52, 34–43.
6. Q. F. Yao, T. K. Chen, X. Yuan and J. P. Xie, Acc. Chem. Res., 2018, 51, 1338–1348.
7. Q.-F. Zhang, X. Chen and L.-S. Wang, Acc. Chem. Res., 2018, 51, 2159–2168.
8. Y. Z. Lu and W. Chen, Chem. Soc. Rev., 2012, 41, 3594–3623.
9. S. Wang, S. Jin, S. Yang, S. Chen, Y. Song, J. Zhang and M. Zhu, Sci. Adv., 2015, 1, e1500441.
10. L. Tang, Y. Luo, X. Ma, B. Wang, M. Ding, R. Wang, P. Wang, Y. Pei and S. Wang, Angew. Chem., Int. Ed., 2023, 62, e202300553.
11. L. Tang, A. Ma, C. Zhang, X. Liu, R. Jin and S. Wang, Angew. Chem., Int. Ed., 2021, 60, 17969–17973.
12. Y. Yun, H. Sheng, K. Bao, L. Xu, Y. Zhang, D. Astruc and M. Zhu, J. Am. Chem. Soc., 2020, 142, 4126–4130.
13. S. Wang, X. Meng, A. Das, T. Li, Y. Song, T. Cao, X. Zhu, M. Zhu and R. Jin, Angew. Chem., Int. Ed., 2014, 53, 2376–2380.
14. X. Wang, B. Yin, L. Jiang, C. Yang, Y. Liu, G. Zou, S. Chen and M. Zhu, Science, 2023, 381, 784–790.
15. A. Ma, J. Wang, Y. Wang, Y. Zuo, Y. Ren, X. Ma and S. Wang, Polyoxometalates, 2024, 3, 9140054.
16. H. Shen, L. Wang, O. López-Estrada, C. Hu, Q. Wu, D. Cao, S. Malola, B. K. Teo, H. Häkkinen and N. Zheng, Nano Res., 2021, 14, 3303–3308.
17. Y. Li, H. K. Kim, R. D. McGillicuddy, S.-L. Zheng, K. J. Anderton, G. J. Stec, J. Lee, D. Cui and J. A. Mason, J. Am. Chem. Soc., 2023, 145, 9304–9312.
18. S. K. Barik, T.-H. Chiu, Y.-C. Liu, M.-H. Chiang, F. Gam, I. Chantrenne, S. Kahlal, J.-Y. Saillard and C. W. Liu, Nanoscale, 2019, 11, 14581–14586.
19. H. Chen, L. Peng, Y. Bian, X. Shen, J. Li, H.-C. Yao, S.-Q. Zang and Z. Li, Appl. Catal., B, 2021, 284, 119704.
20. L. Tang, X. Kang, X. Wang, X. Zhang, X. Yuan and S. Wang, Inorg. Chem., 2021, 60, 3037–3045.
21. R. Itteboina, U. D. Madhuri, P. Ghosal, M. Kannan, T. K. Sau, T. Tsukuda and S. Bhardwaj, J. Phys. Chem. A, 2018, 122, 1228–1234.
22. Y. Negishi, H. Horihata, A. Ebina, S. Miyajima, M. Nakamoto, A. Ikeda, T. Kawawaki and S. Hossain, Chem. Sci., 2022, 13, 5546–5556.
23. Y. Tan, Y. Lv, L. Xu, Q. Li, J. Chai, S. Yang, H. Yu and M. Zhu, J. Am. Chem. Soc., 2023, 145, 4238–4245.
24. S. Chen, S. Wang, J. Zhong, Y. Song, J. Zhang, H. Sheng, Y. Pei and M. Zhu, Angew. Chem., Int. Ed., 2015, 54, 3145–3149.
25. A. Ma, W. Du, J. Wang, K. Jiang, C. Zhang, W. Sheng, H. Zheng, R. Jin and S. Wang, J. Phys. Chem. Lett., 2023, 14, 5095–5101.
26. K. R. Krishnadas, A. Ghosh, A. Baksi, I. Chakraborty, G. Natarajan and T. Pradeep, J. Am. Chem. Soc., 2016, 138, 140–148.
27. K. R. Krishnadas, A. Baksi, A. Ghosh, G. Natarajan and T. Pradeep, Nat. Commun., 2016, 7, 13447.
28. L. Xu, Q. Li, T. Li, J. Chai, S. Yang and M. Zhu, Inorg. Chem. Front., 2021, 8, 4820–4827.
29. Y.-D. Cao, D. Yin, S. Li, X.-Y. Dong, Y. Feng, H. Liu, L.-L. Fan, G.-G. Gao and S.-Q. Zang, Angew. Chem., Int. Ed., 2023, 62, e202307678.
30. H. Shan, J. Shi, T. Chen, Y. Cao, Q. Yao, H. An, Z. Yang, Z. Wu, Z. Jiang and J. Xie, ACS Nano, 2023, 17, 2368–2377.
31. X. Wei, X. Kang, Z. Zuo, F. Song, S. Wang and M. Zhu, Natl. Sci. Rev., 2020, 8, nwaa077.
32. S. Chen, W. Du, C. Qin, D. Liu, L. Tang, Y. Liu, S. Wang and M. Zhu, Angew. Chem., Int. Ed., 2020, 59, 7542–7547.
33. C. J. Zeng, C. Y. Liu, Y. Pei and R. C. Jin, ACS Nano, 2013, 7, 6138–6145.
34. M. S. Bootharaju, C. P. Joshi, M. J. Alhilaly and O. M. Bakr, Chem. Mater., 2016, 28, 3292–3297.
35. H. W. Dong, L. W. Liao and Z. K. Wu, J. Phys. Chem. C, 2017, 8, 5338–5343.
36. A. Baghdasaryan, E. Brun, Y. Wang, G. Salassa, J. Lacour and T. Buergi, Chem. Sci., 2021, 12, 7419–7427.
37. C. L. Heinecke, T. W. Ni, S. Malola, V. Makinen, O. A. Wong, H. Hakkinen and C. J. Ackerson, J. Am. Chem. Soc., 2012, 134, 13316–13322.
38. Z. H. Tang, T. Ahuja, S. M. Wang and G. L. Wang, Nanoscale, 2012, 4, 4119–4124.
39. W. Du, S. Jin, L. Xiong, M. Chen, J. Zhang, X. Zou, Y. Pei, S. Wang and M. Zhu, J. Am. Chem. Soc., 2017, 139, 1618–1624.
40. X. Zou, X. Kang and M. Zhu, Chem. Soc. Rev., 2023, 52, 5892–5967.
41. H. F. Qian, D. E. Jiang, G. Li, C. Gayathri, A. Das, R. R. Gil and R. C. Jin, J. Am. Chem. Soc., 2012, 134, 16159–16162.
42. Y. Niihori, W. Kurashige, M. Matsuzaki and Y. Negishi, Nanoscale, 2013, 5, 508–512.
43. T. Dainese, S. Antonello, S. Bogialli, W. W. Fei, A. Venzo and F. Maran, ACS Nano, 2018, 12, 7057–7066.
44. Y. A. Wang, B. Nieto-Ortega and T. Burgi, Chem. Commun., 2019, 55, 14914–14917.
45. X. W. X. Kang, S. Jin, S. Wang and M. Zhu, CCS Chem., 2021, 3, 1929–1939.
46. J.-H. Yu, Z.-R. Yuan, J. Xu, J.-G. Wang, M. Azam, T.-D. Li, Y.-Z. Li and D. Sun, Chem. Sci., 2023, 14, 6564–6571.
47. J. Z. Yan, H. F. Su, H. Y. Yang, S. Malola, S. C. Lin, H. Hakkinen and N. F. Zheng, J. Am. Chem. Soc., 2015, 137, 11880–11883.
48. K. H. Wijesinghe, N. A. Sakthivel, T. Jones and A. Dass, J. Phys. Chem. C, 2020, 11, 6312–6319.
49. H. Shen, E. Selenius, P. Ruan, X. Li, P. Yuan, O. Lopez-Estrada, S. Malola, S. Lin, B. K. Teo, H. Häkkinen and N. Zheng, Chem.–Eur. J., 2020, 26, 8465–8470.
50. Q. Z. Li, S. Yang, T. Chen, S. Jin, J. S. Chai, H. Zhang and M. Z. Zhu, Nanoscale, 2020, 12, 23694–23699.
51. C. Zhu, T. Duan, H. Li, X. Wei, X. Kang, Y. Pei and M. Zhu, Inorg. Chem. Front., 2021, 8, 4407–4414.
52. S. Wang, Y. Tan, T. Li, Q. Zhou, P. Li, S. Yang, H. Yu and M. Zhu, Inorg. Chem., 2022, 61, 18450–18457.
53. C. Zeng, T. Li, A. Das, N. L. Rosi and R. Jin, J. Am. Chem. Soc., 2013, 135, 10011–10013.
54. A. Ma, J. Wang, J. Kong, Y. Ren, Y. Wang, X. Ma, M. Zhou and S. Wang, Phys. Chem. Chem. Phys., 2023, 25, 9772–9778.
55. N. A. Sakthivel, M. Stener, L. Sementa, M. Medves, G. Ramakrishna, A. Fortunelli, A. G. Oliver and A. Dass, J. Phys. Chem. C, 2019, 123, 29484–29494.
56. C. Kumara, C. M. Aikens and A. Dass, J. Phys. Chem. Lett., 2014, 5, 461–466.

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Footnote

† Electronic supplementary information (ESI) available: Details of the experiment, characterization and supporting figures. CCDC 2327471–2327473. For ESI and crystallographic data in CIF or other electronic format see DOI: https://doi.org/10.1039/d4ra01274g

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