  There is rising interest on low-k dielectric materials based on porous
metal-organic frameworks (MOFs) for improved electrical insulation in
microelectronics. Herein, we demonstrate the concept of MOF dielectric sensor
built from a single crystal of HKUST-1. We study guest encapsulation effects of
polar and non-polar molecules, by monitoring the transient dielectric response
and AC conductivity of the crystal exposed to different vapors (water, I2,
methanol, ethanol). The dielectric properties were measured along the <100>
crystal direction in the frequency range of 100 Hz to 2 MHz. The dielectric
data show the efficacy of MOF dielectric sensor for discriminating the guest
analytes. The time-dependent transient response reveals dynamics of the
molecular inclusion and exclusion processes in the nanoscale pores. Since
dielectric response is ubiquitous to all MOF materials (unlike DC conductivity
and fluorescence), our results demonstrate the potential of dielectric MOF
sensors compared to resistive sensors and luminescence-based approaches.
