| The ventilation system in modern buildings can adjust indoor temperature and humidity,create good indoor air quality,create a good working and living environment,and the quality of indoor air quality is inseparable from human health.However,ventilation systems are also one of the sources of microbial aerosol pollution,and have been included in the category of indoor air pollutants by the World Health Organization,of which bacterial aerosols account for the largest proportion.The humidifier,heat exchange coil,ventilation duct and other components of the ventilation system have a humid and hot microenvironment that provides conditions for bacteria to multiply.The air sent to the room cannot avoid contact with the ventilation system,and if the air is polluted,it may pollute the entire indoor environment through the ventilation duct,increasing the risk of respiratory diseases such as colds,rhinitis,pneumonia and so on.Traditional antibacterial materials,such as chitosan,metal oxides,metal salts,etc.,have defects such as poor heat resistance,low antibacterial aging,and need to be sterilized under ultraviolet irradiation.Therefore,the development of antibacterial materials with long antibacterial aging and strong antibacterial activity has become the research direction of many scholars.Metal organic frameworks（MOFs）are a kind of porous composite materials composed of metal ions or metal clusters and organic ligands,which have the advantages of large specific surface area,high porosity,adjustable structure and modification.MOFs are regarded as the third generation of new antibacterial materials,and their metal sites can continuously and slowly release metal ions to achieve long-lasting antibacterial effects,and organic ligands also have good antibacterial activity and biocompatibility.In this study,bimetallic Co-Cu-BTC materials based on MOFs materials and Cu-BTC materials supported metal nanoparticles were independently developed.In order to elucidate the relationship between structural properties and antimicrobial activity,antimicrobial materials were characterized.Using Bacillus subtilis as the experimental strain,the minimum inhibitory concentration and antibacterial circle of the materials were tested,and the antibacterial properties of the two types of antibacterial materials were evaluated.（1）Bimetallic organic framework Cox/Cu-BTC with different metal Co loading was prepared by hydrothermal synthesis combined with ultrasonic assistance,and the effect of different metal Co doping amounts on antibacterial activity was explored.Through a series of characterization methods,the surface morphology,phase composition,functional groups,void structure and other physical and chemical properties of Cu-BTC and bimetallic organic framework Cox/Cu-BTC were characterized.The results showed that the doping of metal Co improved the stability of the antibacterial material,and Cox/Cu-BTC still maintained the crystal structure of Cu-BTC,and the crystal surface was worm-like.The specific surface areas of Cu-BTC and Cox/Cu-BTC（x=7,14,21,x is the percentage of Co in total metal moles）were 1471.2m2·g-1,1036.1 m2·g-1,652.4 m2·g-1 and 434.4 m2·g-1,respectively.The average pore sizes were1.61 nm,1.63 nm,1.73 nm,and 2.34 nm,respectively.Doping of Co changes the ordered pore structure of Cu-BTC,resulting in a larger pore size.（2）The minimum inhibitory concentrations of Cu-BTC and Cox/Cu-BTC（x=7,14,21）were 1.25 mg/m L,1.25 mg/m L,1.25 mg/m L,and 2.5 mg/m L,respectively.When cultured to18 h,the inhibition circle diameters of Cu-BTC and Cox/Cu-BTC were 22.01 mm,21.4 mm,20.89 mm and 20.70 mm,respectively.There are two metal elements,Co and Cu,in bimetallic Cox/Cu-BTC,and its antibacterial activity is generated by releasing Cu2+and Co2+interacting with the cell membrane of bacteria.Since the antibacterial effect of Co element is not as strong as that of Cu element,the antibacterial activity of Cox/Cu-BTC gradually decreases with the increase of the doping modification amount of Co,and Co and Cu in Cox/Cu-BTC do not produce synergistic antibacterial effect.（3）Using the post-synthetic exchange method,Ag nanoparticles（NPs）with different molar ratios were dispersed and loaded to Cu-BTC by ultrasound,and Agx/Cu-BTC（x=7,14,21,x is the percentage of Ag in total metal moles）were obtained.The physicochemical properties and antibacterial activity of Agx/Cu-BTC were explored.X-ray diffraction analysis（XRD）,X-ray spectroscopy（EDX-Mapping）,X-ray photoelectron spectroscopy（XPS）and other characterization results proved the existence of metal Ag element,and also verified the successful loading of Ag NPs,and Agx/Cu-BTC retained the regular octahedral structure of Cu-BTC.Unlike Cu-BTC,the surface of Agx/Cu-BTC crystals is attached by disordered fibrous filament,and the specific surface area of the material gradually decreases with the increase of Ag molar ratio,and the specific surface areas of Cu-BTC and Agx/Cu-BTC are 1471.2 m2·g-1,1341.1 m2·g-1,1010.3 m2·g-1,and 991.5 m2·g-1,respectively.Cu elements in Agx/Cu-BTC exist in the valence state of Cu0 and Cu2+,and Ag elements exist in the form of Ag0.（4）The minimum inhibitory concentration values of Cu-BTC and Agx/Cu-BTC（x=7,14,21）were 1.25 mg·m L-1,0.6250 mg·m L-1,0.3125 mg·m L-1,and 0.3125 mg·m L-1,respectively,among which the antibacterial effect of Agx/Cu-BTC series was stronger than that of Cu-BTC.The inhibition circle results showed that the inhibition circle sizes of Cu-BTC and Agx/Cu-BTC were 21.6 mm,23.26 mm,24.01 mm and 24.60 mm respectively when the bacteria were cultured to 18 h.Agx/Cu-BTC series are stronger than Cu-BTC antibacterial activity.The Ag+released by Ag NPs crosses the cell membrane and enters the cell to produce reactive oxygen species（ROS）,which increases the ROS level,resulting in cell damage or death,and the greater the concentration of Ag NPs,the stronger the antibacterial activity.The Cox/Cu-BTC and Agx/Cu-BTC independently prepared in this study have certain antibacterial activity,which has actively explored the application of new modified MOFs in the field of built environment and energy application engineering,and effectively promoted the innovation and research and development of new antibacterial materials. |
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