A Highly Stable Two‐Dimensional Copper(II) Organic Framework for Proton Conduction and Ammonia Impedance Sensing

Abstract

Abstract This work reports the design and fabrication of a proton conductive 2D metal–organic framework (MOF), [Cu( p ‐IPhHIDC)] n ( 1 ) ( p ‐IPhH 3 IDC=2‐( p ‐ N ‐imidazol‐1‐yl)‐phenyl‐1 H ‐imidazole‐4,5‐dicarboxylic acid) as an advanced ammonia impedance sensor at room temperature and 68–98 % relative humidity (RH). MOF 1 shows the optimized proton conductivity value of 1.51×10 −3 S cm −1 at 100 °C and 98 % RH. Its temperature‐dependent and humidity‐dependent proton conduction properties have been explored. The large amount of uncoordinated carboxylate groups between the layers plays a vital role in the resultant conductivity. Distinctly, the fabricated MOF‐based sensor displays the required stability toward NH 3 , enhanced sensitivity, and notable selectivity for NH 3 gas. At room temperature and 68 % RH, it gives a remarkable gas response of 8620 % to 130 ppm NH 3 gas and lower detection limit of 2 ppm towards NH 3 gas. It is also found that the gas response of the ammonia sensor increases linearly with the increase of NH 3 gas concentration under 68–98 % RH and room temperature. Moreover, the sensor indicates excellent reversibility and selectivity toward NH 3 versus N 2 , H 2 , O 2 , CO, CO 2 , benzene, and MeOH. Based on structural analyses, activation energy calculations, water and NH 3 vapor absorptions, and PXRD determinations, proton conduction and NH 3 sensing mechanisms are suggested.