Medium-entropy state quinary keplerate clusters as a remarkable electrocatalyst for small molecule electrooxidation

The synthesis of discrete polyoxometalate clusters composed of more than 3 metallic elements has always been attractive but seldom successful. For the first time, we have developed a de novo synthetic route to quinary Cu-Ni-Co-Mn-Zn Keplerate clusters with a nuclearity of 20. Seven single-crystalline quinary Keplerates in a medium-entropy state with various compositions have been obtained. A systematic study reveals that the different ions' ability to be incorporated into the Keplerates is governed by the Irving-Williams series, and they are stabilized in a medium entropy state. More intriguingly, these quinary Keplerate clusters represent an analogue of the Ship of Theseus at the molecular level, i.e., the global features of the {M-20} Keplerates are intact, while the constitution can be altered by tuning the synthesis conditions. Our further investigation reveals that the quinary elements {M-20} compared to mono-component and binary Keplerate clusters exhibit much superior electrochemical performance, therefore shedding light on the design of multimetallic clusters in high-entropy states as novel electrocatalysts.