| One of the main components of indoor air pollutants is volatile organic compounds(VOCs).VOCs not only have a pungent odor,but also cause great harm to the environment and human health.Therefore,it is of great significance to develop a functional material that can detect and degrade VOCs.Leather is widely used in households due to its advantages of softness and breathability.The performance of fluorescent sensing and photocatalytic degradation of VOCs can be imparted to leather by coating materials,which can effectively prevent the human from being in a polluted environment for a long time and solve the problem of indoor pollution.In this paper,a bifunctional coating material with both fluorescence sensing and photocatalytic degradation properties for VOCs was obtained by using polyacrylate(PA)as the matrix and modified UiO-66 as the functional filler,and applied it to leather finishing.First,UiO-66 with fluorescence properties was prepared by solvothermal method,and the effect of different conjugated structures on its fluorescence properties was investigated;Secondly,UiO-66-TBPE with AIE effect was prepare by carboxylated tetraphenylethylene(TBPE)with aggregation-induced emission(AIE)as a ligand,and the effect of different synthesis conditions on the fluorescence sensing performance of VOCs was investigated,and its fluorescence sensing mechanism for VOCs was proposed;Finally,UiO-66-TBPE/TiO2/PA leather coating material with both fluorescence sensing and photocatalytic degradation performance for VOCs was prepared by introduce TiO2.The effects of the preparation process of UiO-66-TBPE and TiO2 on the fluorescence sensing and photocatalytic degradation performance of VOCs were investigated,and its application was proposed.The specific research contents are as follows:(1)UiO-66 was prepared by solvothermal method.By introducing-NH2,-SO3H,-CH=CH2 into the ligands,the effects of different conjugated structures of the ligands on the fluorescence properties of UiO-66 were investigated.The results show that the UiO-66-SO3H with both p-π and π-π conjugation in the ligand has the best fluorescence performance.UiO-66 and modified UiO-66-x were introduced into PA,and the optimal preparation process was obtained based on the fluorescence properties and mechanical properties of the composite films.The experimental results show that the UiO-66-SO3H/PA composite film has the best fluorescence properties,and the introduction of UiO-66 and UiO-66-x can enhance the mechanical properties and water vapor permeability of the PA film.The reasons for UiO-66 and UiO-66-x enhance the mechanical properties and water vapor permeability of PA composite films are explained from the molecular level by computer simulation.The UiO-66/PA and UiO-66-x/PA composite emulsions were applied to leather finishing,the results showed that compared with the leather finished with PA emulsion finishing,the physical and mechanical properties and hygienic properties of the leather finished with UiO-66/PA and UiO-66-x/PA composite emulsion were improved.(2)Preparation of carboxylated modified tetraphenylethylene(TBPE)by substitution reaction.UiO-66-TBPE with dual ligands was prepared by using 2-sulfoterephthalic acid(BDC-SO3H)and TBPE as ligands and ZrOCl2 as metal source.The optimal synthesis process was obtained based on the fluorescence properties.UiO-66-TBPE fluorescence sensing experiments show that the use of benzene,toluene,xylene,chlorobenzene,styrene as targets,using the π-πinteraction between UiO-66-TBPE and UiO-66-TBPE can achieve rapid detection of VOCs.Among them,the fluorescence sensing sensitivity of p-xylene and styrene is the best.The UiO-66-TBPE/PA composite film was prepared by introducing UiO-66-TBPE into the PA,and the optimal preparation process was obtained based on the fluorescence performance.Fluorescence sensing experiments show that the UiO-66-TBPE/PA composite film retains a relatively sensitive sensing behavior for VOCs such as toluene,which styrene has excellent fluorescence sensing sensitivity and stability,the detection limit is as low as 0.76 ppm.The UiO-66-TBPE/PA composite emulsion was used for leather finishing and the finishing process was optimized.The results show that the leather finished with blending emulsion has better fluorescence performance,and retains the fluorescence sensing behavior of VOCs and has the best fluorescence sensing sensitivity to styrene.(3)The preparation method of TiO2 was optimized with the specific surface area as the index,and it was compounded with UiO-66-TBPE,and the optimal preparation process was obtained with the photocatalytic degradation performance as the index.By FT-IR and XPS,it is proved that there is a good interfacial interaction between the UiO-66-TBPE and TiO2,which is beneficial to the effective separation of electrons and holes.Fluorescence sensing and photocatalytic degradation experiments show that UiO-66-TBPE/TiO2 has both fast fluorescence response and good photocatalytic degradation activity to toluene,and the degradation rate is as high as 96%.And it still has strong photocatalytic activity for the target after 10 degradation cycles,and has excellent photocatalytic stability.UiO-66-TBPE/TiO2 was introduced into PA,and the amount of UiO-66-TBPE/TiO2 was optimized to be 13%based on the fluorescence properties and photocatalytic degradation properties of UiO-66-TBPE/TiO2 composite films.Fluorescence sensing and photocatalytic degradation experiments show that UiO-66-TBPE/TiO2/PA not only has fast fluorescence sensing performance,but also has good photocatalytic degradation performance for toluene.The UiO-66-TBPE/TiO2/PA composite emulsion was used for leather finishing,and the finished-leather were tested for fluorescence sensing performance and photocatalytic degradation performance.The results showed that the finished-leather still had excellent fluorescence sensing performance and photocatalytic performance catalytic degradation performance.(4)Based on the previous experimental results,the possible mechanisms of fluorescence sensing and photocatalytic degradation in this study were discussed.First,the possible mechanism of fluorescence sensing of VOCs by UiO-66-TBPE was explored.For the fluorescence enhancement mechanism,the PL results show that when UiO-66-TBPE is sensing with xylene,π-π interactions occur between xylene and the uninhibited benzene ring in the UiO-66-TBPE framework structure,it affects the uninhibited benzene ring conformation in the UiO-66-TBPE system,resulting in enhanced fluorescence.For the phenomenon of fluorescence mechanism,XRD,PL and computational simulation results show that the highest occupied molecular orbital(LUMO)of UiO-66-TBPE is higher than the LUMO orbital of styrene.The charge transfer pathway from UiO-66-TBPE to styrene is opened based on photoinduced electron transfer(PET),resulting in weakened fluorescence.Secondly,taking toluene as an example,the possible mechanism of the photocatalytic degradation of VOCs by UiO-66-TBPE/TiO2 was proposed.It was confirmed by BET,EIS and ESR analysis that the good interfacial compatibility of UiO-66-TBPE/TiO2 and the synergistic effect of more adsorption sites can accelerate the entry of reactants into active sites and effectively shorten the "adsorption-catalysis" pathway.More importantly,UiO-66-TBPE/TiO2 possesses remarkable separation properties and a potential process of photoinduced carrier migration,which degrades toluene to CO2 and H2O via ·O2-and ·OH radicals formed by photogenerated electrons and holes.Finally,the interaction mechanism between the fluorescence sensing performance and the photocatalytic degradation performance was established,and there is a linear relationship between the difference in fluorescence intensity(the fluorescence intensity of UiO-66-TBPE/TiO2 containing toluene compared with that of pristine UiO-66-TBPE/TiO2)and the degradation rate. |
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