In situ thermal-induced generation of{Ag^(0)Ag^(Ⅰ)}dimer within Co-Ag phosphonates

摘要

The thermal decomposition of Ag NO_(3)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[Ag_(2)^(Ⅰ)Co_(2)^(Ⅲ)(notp H_(3))_2(NO_(3))]X[X=NO_(3)^(-)(1)or Cl O_(4)^(-)(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(notp H_(3))and NO_(3)^(-) anion.The number of Ag(Ⅰ)ions connected to each NO_(3)^(-) anion reduces from 5 in bulk Ag NO_(3) to 2 in compounds 1 and 2,leading to the Ag NO_(3)component stepwise decomposition at a lower temperature(<300℃).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℃for 1 and 254℃for 2).