Synthesis and characterization of Ag(I) alkynyl nanoclusters utilizing Mo <sup>VI</sup>-anchored thiacalix[4]arene metalloligands: Application in electrocatalytic CO <sub>2</sub> reduction
Shang-Qian Li, Liangjun Li, Yi-Qi Tian, Wen-Lei Mu, Ru-Xin Meng, Jun Yan, Chao Liu
Abstract
The utilization of metalloligands as building blocks for assembling heteronuclear metallocages or heterometallic coordination polymers has garnered increasing attention, yet its utilization for the assembly of Ag(I) alkynyl nanoclusters remains limited.<strong> </strong>Herein we present the synthesis of two new Ag(I) alkynyl nanoclusters, namely <strong>Mo<sub>2</sub>Ag<sub>8</sub></strong> and <strong>Mo<sub>2</sub>Ag<sub>12</sub></strong>, employing a Mo<sup>VI</sup>O<sub>2</sub>R-anchored (R= O or OEt) thiacalix[4]arene (TC4A) as a metalloligand. Through detailed structural analysis, their distinct sandwich geometries were revealed. <strong>Mo<sub>2</sub>Ag<sub>8</sub></strong> features a square Ag<sub>4</sub>(<sup>t</sup>BuC≡C)<sub>4</sub> core enclosed between two {MoAg<sub>2</sub>-TC4A} units, with two MoO<sub>2</sub>(OEt) units suspended on each side of the cluster. <strong>Mo<sub>2</sub>Ag<sub>12</sub></strong> exhibits a hexagonal Ag<sub>6</sub>(<sup>t</sup>BuC≡C)<sub>6</sub> core sandwiched between two {MoAg<sub>3</sub>-TC4A} units, with two MO<sub>3</sub> units acting as oxygen anion templates that directly interact with Ag(I) ions. Furthermore, we demonstrated the electrocatalytic application of these Ag-Mo bimetallic clusters for CO<sub>2</sub> reduction. The catalytic results revealed that the binding mode of MO<sub>3</sub> units significantly influenced the electrochemical CO<sub>2</sub> reduction (eCO<sub>2</sub>RR) activity and the competitive hydrogen evolution reaction (HER) activity of the clusters. Notably, <strong>Mo<sub>2</sub>Ag<sub>12</sub></strong> achieved an impressive Faradaic efficiency (FE) of 60.85% for CO production at a voltage of -0.8 V (vs RHE).