In situ thermal-induced generation of {Ag0AgI} dimer within Co-Ag phosphonates

Abstract

The thermal decomposition of AgNO3 is known to produce metallic Ag, but single-atomic dispersion is hard to achieve instead of the aggregation state of nanoparticles. Herein, we develop an efficient approach to thermally generate and stabilize single Ag atoms via the coordination effect. Two desired Co-Ag phosphonates [AgI2CoIII2(notpH3)2(NO3)]X [X = NO3− (1) or ClO4− (2)] were synthesized by solid-phase grinding method or solution crystallization. Both crystal structures reveal slightly different packing arrangements of various lattice anions and identical one-dimensional (1-D) coordination chains, formed in each case by the coordination of Ag(I) to the metalloligand Co(notpH3) and NO3− anion. The number of Ag(I) ions connected to each NO3− anion reduces from 5 in bulk AgNO3 to 2 in compounds 1 and 2, leading to the AgNO3 component stepwise decomposition at a lower temperature (<300 °C). During the thermal decomposition, the changes of supermolecular structures and Ag oxidation states were monitored by PXRD, IR and XAFS measurements. The most interesting finding is that 1 and 2 can retain chain structures and harvest Ag(0) atoms in the chain by controlling decomposition temperatures (220 °C for 1 and 254 °C for 2).