C≡C Or C≡N Bond Facilitated Low-Temperature CO Catalytic Oxidation

With the rapid development of the global economy and modern industrial production,a large amount of pollutants such as carbon monoxide(CO)are becoming the major source of air pollution especially in mega cities,which have caused serious problems to human health and the environment.Catalytic purification is an important technology for the removal of gaseous pollutants,wherein the catalytic oxidation is the key step.However,the commercial catalysts,which are used for catalytic oxidation of CO and other gaseous pollutants at low temperatures,still face some challenges,such as high amount of usage of noble metal and the lack of optimized structure.Therefore,it is urgent to develop a highly efficient catalyst with lower noble metal usage but improved catalytic activity for air pollution control.Organic-based nano-catalysts have attracted a wide attention for low-temperature heterogeneous catalysis because of their low cost,high selectivity,high activity and excellent molecular tunability.Compared with the inorganic catalysts,the stability of organic catalysts is poor due to self-oxidation.Density functional theory(DFT)calculations have predicted that the transition metal-mediated triple bond(e.g.,C≡N bond and C≡C bond)could improve the stability of the triple bond and the activation of molecular oxygen(O2).Thus,the organic materials containing metal-coordinated triple bonds may be high-efficiency catalysts for low-temperature oxidation reactions.Based on this,we designed and synthesized an organic nano-catalyst with C≡N bond or C≡C bond to study its low-temperature catalytic oxidation performance and catalytic reaction mechanism by using CO as a probe molecule.The specific research contents of this dissertation are as follows:The CuTCNQ nanowires(CuTCNQ NWs)array uniformly grown on the copper foam were synthesized through a simple organic vapor-solid-phase reaction.We firstly reported that the well-defined CuTCNQ NWs exhibits higher catalytic performance for CO oxidation.DFT calculations and electron paramagnetic resonance(EPR)spectra results reveal that the molecular O2 is preferentially activated on the Cu(I)-mediated C≡N bond and then reduced to superoxide radical anion(·O2-)via one-electron transfer.The in-situ diffuse reflectance infrared Fourier transform spectra(DRIFTS)results demonstrate that the CO molecule directly reacts with the·O2-to form carbon dioxide(CO2)by Eley-Rideal(E-R)mechanism.The graphdiyne composite catalyst modified by cobalt was prepared via impregnation and calcination.The as-prepared catalysts were also studied for low-temperature catalytic oxidation of CO.The transmission electron microscopy(TEM)and X-ray photoelectron spectroscopy(XPS)results demonstrate that metallic cobalt-modified graphdiyne can serve as a promising catalyst for efficient oxidation of CO.The considerable catalytic activity may be due to the interaction between metallic cobalt and graphdiyne.Oxygen temperature programming desorption(O2-TPD)indicates that the surface of Co/Graphdiyne catalyst possesses abundant reactive oxygen species(ROS),which facilitate the CO catalytic oxidation at low temperature.In summary,the construction of transition metal-mediated C≡N bond and C≡C bond contributes to the molecular O2 activation,thus facilitating the low-temperature CO oxidation.Our work pave a new avenue for rational design of high-efficiency organic-based metal heterogeneous catalysts with low-cost for air pollution control at low temperatures.