Calixarene-Based {Ni18} Coordination Wheel: Highly Efficient Electrocatalyst for the Glucose Oxidation and Template for the Homogenous Cluster Fabrication.

Catalyst plays a very important role in the exploration of new energy. To obtain a highly efficient electrocatalyst for the glucose oxidation and tiny metal nanocluster catalysts, a calixarene-based {Ni18} coordination wheel with sulfur atoms on the cavity surface was designed, synthesized, and used as the porous template. Contributing from the active sites of nickel cations, the as-synthesized coordination wheels can efficiently catalyze the electrochemical oxidation of glucose with the onset and peak potentials of 0.3 and 0.46 V in alkaline medium, and the catalysis does not depend on the atmosphere (N2, air, or O2), which indicates that the coordination wheel will be a promising electrocatalyst candidate for the compartmentless glucose-air fuel cell. Meanwhile, benefiting from its confined cavity and inner sulfur surface, such a coordination wheel can serve as a general template for the fabrication and encapsulation of tiny metal nanoclusters of Au, Pd, Ir, Ru, Rh, Pt, and AuPd. In electrochemical examinations, the bimetallic AuPd clusters confined in the coordination wheel show higher current density than commercial Pt/C toward hydrogen evolution reaction (HER). The present study shows that the designed coordination wheel can be used as not only a type of novel catalyst itself but also a class of templates for metal cluster catalysts.