Superconducting Two-Dimensional Metal-Organic Framework*

Superconductivity is a fascinating quantum phenomenon characterized by zero electrical resistance and the Meissner effect. To date, several distinct families of superconductors (SCs) have been discovered. These include 3D bulk SCs in both inorganic and organic materials as well as 2D thin film SCs but only in inorganic materials. Here we predict superconductivity in 2D and 3D organic metal-organic frameworks by using first-principles calculations. We show that the highly conductive and recently synthesized Cu-benzenehexathial (BHT) is a Bardeen-Cooper-Schrieffer SC. Remarkably, the monolayer Cu-BHT has a critical temperature (T_c) of 4.43 K while Tc of bulk Cu-BHT is 1.58 K. Different from the enhanced T_c in 2D inorganic SCs which is induced by interfacial effects, the T_c enhancement in this 2D organic SC is revealed to be the out-of-plane soft-mode vibrations, analogous to surface mode enhancement originally proposed by Ginzburg. Our findings not only shed new light on better understanding 2D superconductivity, but also open a new direction to search for SCs by interface engineering with organic materials.