Atomically precise Ag nanoclusters intercalated in zirconium pyrophosphate for efficient hydrogenation of nitroaromatics

Designing and fabricating catalysts with highly dispersed metal nanoclusters (NCs) is very crucial for achieving high activity and selectivity. In this work, all-alkynyl-protected [Ag₇₄(C≡CPh)₄₄](NO₃)₂ cluster (Ag cluster) with a well-defined structure was firstly intercalated in α-zirconium phosphate (α-ZrP) through ion-exchange. Then the atomically precise Ag cluster can be immobilized robustly in the support by a sequential process of carbonization, calcination and reduction. The supported Ag cluster showed the relatively high catalytic activity (TOF=222.9-445.8 h⁻¹) and excellent recyclability for hydrogenation of a variety of nitroaromatics, as well as the compounds with carbon-carbon double bonds even if the loading of Ag was as low as 0.72 wt.%. Zirconium pyrophosphate acts as not only a stabilizer of Ag cluster through a spatial confinement, but also an adsorption site for nitroaromatics. The residual carbon arisen from thermal decomposition of all-alkynyl ligand coordinating on Ag cluster exerted an important role in protecting Ag cluster from sintering. As a result, the intercalation of Ag cluster in the interlayer region is a promising strategy for extending their potential applications in catalysis.