Assembly of high-nuclearity Sn26 , Sn34 -oxo clusters: solvent strategies and inorganic Sn incorporation

Abstract

A series of unprecedented high-nuclearity tin-oxo nanoclusters (up to Sn₃₄ ) with structural diversity have been obtained. The characteristics of the applied solvents had great influence on the assembly of these Sn-O clusters. Pure alcohol environments only gave rise to small clusters of Sn₆ , whilst the introduction of water significantly increased the nuclearity to Sn₂₆ , which greatly exceeds those of the known tin-oxo clusters (≤14); the use of aprotic CH₃CN finally produced the largest Sn₃₄ to date. Apart from the nuclearity breakthrough, the obtained tin-oxo clusters also present new structural types that are not found in previous reports, including a layered nanorod-like structure of Sn₂₆ and the cage-dimer structure of Sn₃₄ . The layered Sn₂₆ clusters represent good molecular models for SnO₂ materials. Moreover, an electrode derived from TOC-17 with a {Sn₂₆ } core shows better electrocatalytic CO₂ reduction activity than that from TOC-18 with Sn₃₄ . This work not only provides an efficient methodology for the rational assembly of high-nuclearity Sn-O clusters, but also extends their potential applications in energy conversion.

Fig. 1. The ball-and-stick representations of TOC-12 (a), TOC-13 (b) and TOC-14 (c). Atom color code: green Sn; purple Na; red O; black C; dark blue N; light blue P.

Fig. 2. Polyhedral representations of the Sn₂₆ cluster in TOC-15 (a) and TOC-16 (b). The ball-and-stick representations of Sn₂₆ (c) and SnO₂ (rutile) (d). Polyhedral color code: blue SnO₅C/SnO₃C/SnO₆. Atom color code: green Sn.

Fig. 3. (a) The polyhedral representation of TOC-18. (b) and (c) The ball-and-stick representations of {Sn₁₂} and {Sn₂₂} moieties in TOC-18. Polyhedral color code: blue SnO₅C/SnO₄C/SnO₄NC; purple NaO₇/NaO₆. Atom color code: green Sn; purple Na; red O; black C; dark blue N.

Fig. 4. (a) Linear sweep voltammetry (LSV) of TOC-17 and TOC-18 in Ar or CO₂ saturated 0.5 M KHCO₃ solution. (b) ¹H NMR spectrum of the KHCO₃ catholyte after 3600 s of CO₂ reduction on the TOC-17 derived electrode, E(RHE) = –1.096 V. (c) and (d) The faradaic efficiencies (FE) of formate and CO for TOC-17 and TOC-18 derived electrodes at various potentials.