A honeycomb-layered 2D coordination polymer of [Pb(TMA)]n (H2TMA = 3‑thiophenemalonic acid) for impedimetric humidity sensing with high performance

Abstract

A novel lead-based two-dimensional (2D) coordination polymer of [Pb(TMA)]n (named as PbL, H2TMA = 3-thiophenemalonic acid) was synthesized via a facile precipitation method at room temperature. The PbL shows a 6, 3-connected network of honeycomb topology with thiophene rings on each side of the layer. It is worth noting that unusual PbS weak bonds (3.39 Å) further link the honeycomb layers to generate a three-dimensional (3D) supramolecular framework. Taking inspiration from the 2D lamellar structure and abundant active sites (such as Pb2+ ions, O and S atoms), which will facilitate the adsorption and interaction of water molecules on PbL surface, an impedimetric humidity sensor was fabricated based on this framework. The PbL sensor exhibited high response, good repeatability, small hysteresis, as well as short response and recovery times. Finally, the humidity sensing mechanism of this PbL sensor has been discussed through complex impedance analysis, confirming the contributions of distinct charge carriers at different relative humidity (RH). This work provides a practical candidate for humidity sensors and further develops a new promising application for coordination polymers in electrical sensory devices.