Study On Preparation And Properties Of Porous Gas-sensitive Materials Based On MOFs Structure

Along with the development of social economy and the advance of industrialization,it not only brings convenience to people's life,but also causes great damage to the environment.The increasingly serious pollution problem has seriously hindered the development of the society,making people put forward higher requirements for the efficient monitoring of toxic and harmful gases.In recent years,gas sensors based on porous metal oxide materials derived from metal organic frame structure materials have attracted wide attention due to their unique structural characteristics and good gas sensitivity.Zeolite imidazole skeleton structure?ZIF-8?with zinc as a node is a typical metal organic frame structure,and its derivative zinc oxide?ZnO?has good thermodynamic and chemical stability,as well as the characteristics of easy functionalization,and is widely used in the field of gas sensitive materials.In this paper,ZIF-8 will be doped in situ,metal element doped ZnO nanomaterials will be prepared by subsequent high-temperature calcining process,and ZnO/SnO₂ nanomaterials will be obtained by combining ZIF-8 derived ZnO nanomaterials with electrostatic spinning technology,and the characterization and gas-sensitive performance of the materials are systematically tested.The main findings are as follows:1.ZIF-8 was prepared at room temperature with methanol as the solvent,and ZnO nanometer material was prepared with it as the self-sacrificing template.The morphology,crystal structure and gas-sensitive performance of ZIF-8 derived ZnO nanometer material were studied.Ni doped ZIF-8 nanometer materials were prepared by in-situ doping,and Ni doped ZnO nanometer materials were obtained by subsequent calcining process.The effects of Ni doping and doping amount on the morphology,structure and gas-sensitive properties of the materials were studied.Results show that Ni doping had no significant effect on the material of the morphology and crystal structure,and Ni element can obviously increase the ZIF-8 derived ZnO nanomaterials on H₂S gas sensitive performance,Ni doping amount of 1.5 at%of ZnO nanoparticles on H₂S gas sensitive performance,best under 200?for 5 ppm H₂S sensitivity is 117.8 times of that of without doping,the detection limit of H₂S from 0.5 ppm to 0.01 ppm,selectivity and the response-recovery ability also were improved obviously.2.The ZIF-8 was doped with the rare-earth element La,and the La doped ZnO nanomaterials were obtained by calcining at high temperature.The influences of La doping and doping amount on the microstructure and gas-sensitive properties of ZnO nanomaterials were studied.The results show that La doping is beneficial to obtain spherical nanostructures with smaller particle size,but La doping does not change the crystal structure of ZIF-8 and derived ZnO nanoparticles.With acetone as the target gas La doping of ZnO nanoparticles was studied the influence of gas sensitive performance,found that La doped ZnO nanoparticles can obviously improve sensitivity,selectivity and response-recovery ability of acetone,La doping amount for 3 at%ZnO nanoparticles of acetone gas sensor performance is the best,and at 350?temperature it has good sensitivity;stability and sensitive-acetone concentration linearity.3.ZnO/SnO₂ composite nanofibers were prepared by adding ZIF-8 derived ZnO nanomaterials into the solution of spinning precursor by electrostatic spinning technology,and the morphology,crystal structure and gas-sensitive properties of the composites were studied.Found that ZnO NPs compound SnO₂ nanofibers had no obvious change in diameter and morphology,and ZnO NPs compound SnO₂nanofibers had formed mosaic structure,gas sensitive performance show that ZnO NPs composite significantly increased composite nanofibers of H₂S gas sensitive properties,the compound amount of ZnO NPs reached 5 wt%of ZnO/SnO₂composite nanofibers,the gas sensitive properties of H₂S was optimized,to work in the working temperature of 200?the sensitivity up to 560 for 4 ppm H₂S.And it has excellent selectivity,response recovery ability and sensitivity-gas concentration linear relationship.