Synthesis and characterization of Ag(I) alkynyl nanoclusters utilizing MoVI-anchored thiacalix[4]arene metalloligands: Application in electrocatalytic CO2 reduction

The utilization of metalloligands as building blocks for assembling heteronuclear metallocages or heterometallic coordination polymers has garnered increasing attention, yet its utilization for assembling Ag(I) alkynyl nanoclusters remains limited. In this study, we present the synthesis of two new Ag(I) alkynyl nanoclusters, namely, Mo2Ag8 and Mo2Ag12, employing a MoVIO2R-anchored (R = O or OEt) thiacalix[4]arene (TC4A) as a metalloligand. Through detailed structural analyses, their distinct sandwich geometries were revealed. Mo2Ag8 features a square Ag4(tBuC≡C)4 core enclosed between two {MoAg2–TC4A} units, with two MoO2(OEt) units suspended on each side. Mo2Ag12 features a hexagonal Ag6(tBuC≡C)6 core sandwiched between two {MoAg3–TC4A} units, with two MO3 units acting as oxygen anion templates, directly interacting with Ag(I) ions. In addition, we demonstrated the electrocatalytic application of Ag–Mo bimetallic clusters for CO2 reduction. The catalytic analysis results show that the binding mode of MO3 units considerably influences the electrochemical CO2 reduction activity and competitive hydrogen evolution reaction activity of the clusters. Notably, Mo2Ag12 achieved an impressive Faradaic efficiency of 60.85% for CO production at a voltage of −0.8 V (vs. RHE).