Telltale Diamagnetism at 50 K of a Coordination Polymer System

The synthesis of coordination polymers (e.g., Prussian blue) is as old as modern chemistry, but never stops surprising people. Underlying this rich chemistry is the infinite organic molecules that can be designed to link up various metal ions or clusters. We here report superconductivity observed of a designer coordination polymer system sporting the chemically soft mercaptan and hard carboxyl groups. The mercaptan-carboxyl (dubbed Mercarb, or QiuSuo in Mandarin Pinyin) synergy hints at Daoism and here carries over from the molecular to the solid state: the soft sulfur donors bond with Co2+/Ni2+ (or other transition metal ions) to afford 2D sheets for charge transport, while the interlayer metal-carboxylate domain is more ionic and mediates the transition into the superconductive state. Besides the flexible QiuSuo design, this CP system is open, and allows exchange of molecule guests for tuning the electron-hole balance, in order to achieve high-temperature superconductivity.