(Invited) Photophysics and Electronic Structure of Metal-Organic Frameworks

Abstract

The development of porous crystalline materials such as metal–organic frameworks (MOFs) could add a new dimension to a wide number of applications including supercapacitors, electrodes, or thermoelectrics. From this perspective, the understanding and tailoring of the electronic properties of MOFs are key fundamental challenges that could unlock the full potential of these materials. In the presentation, I will focus on the fundamental insights responsible for the electronic properties of bimetallic systems in which the second metal incorporation occurs through (i) metal replacement in the framework nodes, (ii) metal node extension, and (iii) metal coordination to the organic ligand. Microwave conductivity, X-ray photoelectron spectroscopy, diffuse reflectance spectroscopy, powder X-ray diffraction, inductively coupled plasma atomic emission spectroscopy, pressed-pellet conductivity, and theoretical modeling were imployed to shed light on the key factors responsible for the tunability of MOF electronic structures. Experimental prescreening of MOFs was performed based on changes in the density of electronic states near the Fermi edge, which was used as a starting point for further selection of suitable MOFs. As a result, we demonstrated that the tailoring of MOF electronic properties could be performed as a function of metal node engineering, framework topology, and/or the presence of unsaturated metal sites while preserving framework porosity and structural integrity. These studies unveil the possible pathways for transforming the electronic properties of MOFs from insulating to semiconducting, as well as provide a blueprint for the development of hybrid porous materials with desirable electronic structures.