Selective Gas Sensing under a Mixed Gas Flow with a One-Dimensional Copper Coordination Polymer

Structural changes of the coordination polymer associated with gas adsorption (gate opening-type adsorption) can be linked to bulk physical properties such as magnetism, electrical conductivity, and dielectric properties. To enable real-space sensing applications, it is imperative to have a system where the selective adsorption of mixed gases can be correlated with physical properties. In this report, we demonstrate that a crystalline sample of one-dimensional (1D) coordination polymer exhibits selective CO2 adsorption while simultaneously displaying dielectric switching behavior in a mixed N-2/CO2 gas environment. In the crystal of {[Cu-2(2-TPA)(4)(pz)].CH3CN}n (1.CH3CN), where 2-TPA and pz are 2-thiophencarboxylate and pyrazine, respectively, paddle wheel-type units of [Cu-2(2-TPA)(4)] are bridged by pz, forming a 1D chain structure. One of the two crystallographically independent 2-TPA units was interacted with the pz moiety of the adjacent 1D chain by p...p interactions, forming a two-dimensional (2D) layer parallel to the ab plane. Activated 1 shows selective CO2 adsorption by a gate opening-type adsorption mechanism, indicating that the CO2 adsorption process is accompanied by a structural change. The change in the real part of dielectric permittivity (e') under the mixed N-2/CO2 gas flow is a result of the selective CO2 adsorption, which was supported by the enthalpy changes (?H) associated with CO2 adsorption in two methods: CO2 adsorption isotherms and temperature-dependent measurements of e' under a mixed N-2/CO2 gas flow. The calculated ?H values were found to be in good agreement across both methods. The CO2 ratio in the mixed N-2/CO2 gas flow increased, and the switching ratio of e' (?e') also increased. Notably, ?e' exhibited a marked increase beyond the pressure required for gate opening adsorption.

Automated summary

The structural changes of a coordination polymer associated with gas adsorption can be correlated with physical properties like magnetism, electrical conductivity, and dielectric properties. In this report, a crystalline sample of a one-dimensional coordination polymer is shown to exhibit selective CO2 adsorption and dielectric switching behavior in a mixed N-2/CO2 gas environment. The CO2 adsorption process accompanies a structural change and is supported by the changes in dielectric permittivity and enthalpy associated with CO2 adsorption.