Theoretical Chemistry Study On The Mechanism Of Catalytic Degradation Of Organic Pollutants

With the rapid development of the economy and the advancement of industrialization,the harm of organic pollutants in the environment has become an issue of concern.Porous graphene?PG?is a kind of carbon material with nanoporous,suitable band gap and inherent properties of graphene,so it has great potential in adsorption and photocatalytic degradation of pollutants.Prussian blue analogues?PBAs?are a class of porous coordination polymers with controlled composition and large specific surface area.They are widely used in catalysis,adsorption and gas storage.The purpose of this thesis is to select PG and PBAs as the research objects,and to study the modified PG adsorption and photocatalytic degradation of volatile organic pollutants and the catalytic oxidative degradation of bisphenol A in water by PBAs.The main research contents and results are as follows:?1?The PG monolayer material was modified by metal aluminum.The adsorption and adsorption mechanism of PG and aluminum-modified porous graphene?Al-PG?for oxygen-containing volatile organic compounds?OVOCs?were studied systematically.The results show that PG materials have good adsorption properties for OVOCs.However,the adsorption energy of carbonyl-containing volatile organic compounds?CVOCs?in Al-PG materials is nearly double of that in PG,but other OVOCs do not change much after aluminum modification.Through further analysis of the electronic structure?including PDOS,electron density distribution,and Mulliken charge distribution?,we found that the carbonyl group can attract aluminum atoms through the formation of C-Al bonds,thereby causing bonds between CVOCs and Al-PG substrates during adsorption.It also greatly enhances the adsorption of CVOCs.This work proposes a potential adsorbent for the selective removal of VOCs and provides theoretical guidance for the design of high performance VOCs adsorbents.?2?The PG monolayer material is doped with non-metal sulfur.From the geometrical and electronic properties?including band structure,PDOS and HOMO-LUMO orbitals?,band edge position,adsorption of O₂,H₂O and VOCs,and optical absorption spectra of sulfur-doped porous graphene?S-doped PG?,the photocatalytic degradation of VOCs was discussed.The results show that the doping of sulfur can significantly reduce the band gap of PG material,generate more free electrons and facilitate photo-generated charge separation.S-doped PG has a significant improvement in the adsorption energy of O₂compared to PG and a slight decrease in the adsorption energy of H₂O,which indicates that it improves the ability to generate superoxide radicals and reduces the ability to generate hydroxyl radicals,which is consistent with the band position of the S-doped PG,i.e.,the S-doped PG has a band edge position where superoxide radicals are generated without generating hydroxyl radicals.In addition,S-doped PG has good adsorption properties to VOCs and visible light response.These results indicate that S-doped PG has good photocatalytic activity for typical VOCs degradation.?3?Based on the experimental study of Fenton reaction-activated H₂O₂ for the degradation of bisphenol A by changing the synthesis temperature to synthesize different morphologies of Fe-Co PBAs,we calculated the main exposed crystal faces of Fe-Co PBAs at different temperatures and the adsorption energy and electron transfer of H₂O₂adsorbed by the highly active?100?and?111?faces from the perspective of theoretical chemistry.The results show that the surface energy relationship of the main exposed crystal planes of Fe-Co PBAs at different temperatures is?100?>?111?>?110?,,which indicates that the surface of the crystal with higher surface energy gradually forms as the synthesis temperature increases.In addition,since the adsorbed H₂O₂ has been dissociated into hydroxyl groups on the?100?crystal plane,it provides excellent precondition of the generation of hydroxyl radicals,which indicates that the H₂O₂ activity on the?100?crystal plane is higher.These are all good proofs of the growth behavior of experimental Fe-Co PBAs with the change of synthesis temperature and the influence of crystal on its catalytic activity,which provides a theoretical explanation for the experimental phenomena of organic pollutant degradation.