A 3D pillared-layer cadmium (II) metal-organic framework for chemiresistive humidity sensing with high performance

Abstract

Metal-organic frameworks (MOFs) have been demonstrated to be excellent candidates for gas/humidity sensing applications; however the chemiresistive sensory devices are still rather limited but taking advantages in miniaturization, integration and intelligence. In this contribution, a new cadmium (II) metal-organic framework (MOF) of [Cd(TMA)(DPP)0.5∙H2O]n (noted as CdL, H2TMA = 3‑thiophenemalonic acid, DPP = 1,3‑di(4‑pyridyl)propane) was synthesized via a facile precipitation method at room temperature (RT). The CdL MOF with an unusual 3D pillared-layer structure was characterized by X-ray diffraction and the corresponding chemiresistive humidity sensor was fabricated by coating the powder of CdL on interdigitated electrodes. It is worth noting that the CdL humidity sensor shows high sensitivity, good repeatability, small hysteresis, as well as short response and recovery times. The humidity sensing mechanism of this CdL sensor has been discussed through complex impedance analysis, which reveals that distinct charge carriers make great contributions at different moisture contents. This work provides an alternative candidate material for humidity sensors and further develops a new promising application for MOFs in sensory devices.