Density function theory investigation of bimetallic phthalocyanine as a potential sensor and scavenger for nitrogen-containing toxic gases

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Urbanization and industrialization processes inevitably release a large amount of nitrogen-containing toxic gases (NTGs) such as NO, NO2, NH3 and HCN, posing a serious threat to the ecological environment. Therefore, it is necessary to develop new gas sensors to promptly detect the emission and leakage of these toxic gases. Herein, four bimetallic phthalocyanines (BMPc = FePdPc, FePtPc, MnPdPc and MnPtPc) were designed by introducing pairs of precious metal (Pd/Pt) and inexpensive metal (Fe/Mn) atoms into the phthalocyanine (Pc) monolayer. Subsequently, the adsorption behavior and sensing properties of these BMPc towards NTGs were investigated using density functional theory (DFT) method. The studied results show that the four BMPc exhibit excellent stability and display chemical adsorption for these target gases due to the synergistic effect of bimetallic active centers, with adsorption energy greater than −0.70 eV. The adsorption strength follows the order NO > NO2 > NH3 > HCN, which is further confirmed by electronic properties such as charge density difference and density of states. Additionally, the analyses of work function, bandgap, and sensing response demonstrate the superior sensitivity of BMPc towards NO, NO2, NH3, and HCN. Meanwhile, the MnPtPc monolayer presents suitable adsorption strength for HCN at 298 K, resulting in a short recovery time of only 0.68 s. When the temperature is increased to 348 K, FePdPc and MnPdPc exhibit high reversibility for HCN, while MnPtPc displays favorable performance for NH3. Therefore, MnPtPc is identified as a recyclable HCN gas-sensing material at room temperature, while FePdPc, FePtPc, and MnPdPc are regarded as reusable gas-sensing materials for HCN at high temperature, with their sensing properties remaining unaffected in a humid environment. By contrast, the prolonged recovery times of NOx (x=1, 2) adsorption systems make these four BMPc more suitable as efficient scavengers for NOx. This study provides a new strategy for designing and developing phthalocyanine-based gas sensors and scavengers for the NTGs and other harmful substances.