Towards a Metal-Organic Framework with Pore-Confined Electrons

Abstract

Electrides are an unconventional class of materials in which electrons are localized in crystallographic void spaces rather than solely around atomic nuclei, giving rise to appealing properties such as low work functions, strong electron-donating character, and even superconductivity. Here, we use ab initio methods to investigate metal-organic framework (MOF) electrides, a new class of materials that combines the interstitial electrons of electrides with the permanent porosity and chemical tunability of MOFs. These materials host pore-confined electrons: occupied electronic states localized in the pore space and with bands slightly below or crossing through the Fermi level. Using density functional theory calculations, we establish several design rules for stabilizing pore-confined electrons in MOFs via an anion-electron exchange process and identify candidate MOF electrides. As a proof-of-concept, we also demonstrate that the pore-confined electrons can directly facilitate chemical reactions, substantially lowering the activation barrier for H2 dissociation without requiring adsorption at a surface site. We envision that pore-confined electrons in nanoporous materials may enable a fundamentally new type of catalysis in which chemical reactions take place in the pore space, driven by electron-centered active sites.