Probing Local Donor–Acceptor Charge Transfer in a Metal–Organic Framework Via a Scanning Tunneling Microscope

In an effort to gain more information beyond bulk conductivity of electrically conductive metal–organic frameworks (MOFs), herein, for the first time, we utilize a scanning tunneling microscope (STM) to probe local tunneling conductance in the atomic scale on the surface of conductive MOF-based crystals. By utilizing a porphyrinic zirconium-based MOF installed with electron-donating graphene quantum dots (GQDs) that was published in our recent study as a demonstration, significantly distinct electronic properties can be observed between the locations with and without the GQD–porphyrin donor–acceptor pairs. Such an STM technique is thus considered as a powerful tool to probe the spatial uniformity in electrical conductance and investigate the origins of conductivity for a range of conductive MOF-based materials.