Zr,Ti-based Metal-organic Frameworks (MOFs) Photocatalysts:Preparation,Characterization And Modification

Environmental pollution and energy crisis are two major problems restricting the development of current society.Photocatalytic technology using sunlight directly has been regarded as one of the most effective ways for settling the above issues.But the key lies in the search and design of the efficient and stable photocatalysts.Among various kinds of materials,MOFs have aroused a great interest due to their intriguing physicochemistry properties.MOFs are a class of crystalline materials formed by transition metal-containing clusters as structural nodes bridged by organic linkers.The outstanding properties of MOFs,such as high specific surface area,structural adaptivity and flexibity,make them attractive in heterogeneous catalysis.However,the application of MOFs in photocatalysis is still in their infancy.Based on the principle of crystal engineering,we focused our research on the development of the efficent MOFs photocatalytic materials with high stability and tunable band structures:Tune the band structure of MOFs by modifying the ligands with different substituent groups.Investigate the influence of ligand substituents on the structures,light absorption performance and photocatalytic activity of the pristine material.Study the structure-photoactivity relationships of MOFs photocatalysis.It is of significant values for the study on this project for deeply understanding the intrinsic nature of photocatalysis from molecule level;Optimization the photocatalytic performance of MOFs materials to meet the practical application need,propose the possible mechanism of photocatalytic reaction,and then provide useful insights for future design of novel and more efficient photocatalysts.The details are summarized briefly as follows:(1)By using the 'pre-functionalization' strategy,the amino group was introduced into the skeleton of UiO-66,shifting the photoabsorption edge of UiO-66 from UV light region to the visible light region.Importantly,UiO-66(NH2)is proved to perform as an efficient multifunctional visible-light-driven photocatalyst with high stability and considerable recyclability in both the photocatalytic selective oxidation of alcohols to aldehydes and catalytic reduction of aqueous Cr(?)to Cr(?)under ambient conditions.(2)Modify the property of UiO-66 on molecular level by introducing the functional groups like-NO2,-Br into the skeleton of UiO-66.Study the effect of the functional groups on the band structure,optical absorption and photocatalytic activity of the UiO-66.The as prepared samples have been tested for their photocatalytic activity in water treatment.After further study,the structure-photoactivity has also been established.(3)UiO-66 serves as a matrix for the well-dispersed growth of CdS as well as forms the effective heterostructure with CdS,promoting the fast transfer of photogenerated electrons.MoS2 was deposited on UiO-66/CdS as cocatalyst via a simple and facile photodeposition technique.Without a noble-metal cocatalyst,the obtained MoS2/UiO-66/CdS composites act as high-performance photocatalysts for H2 evolution under visible light irradiation.(4)A simple and flexible electrostatic self-assembly strategy has been developed to fabricate novel photocatalysts RGO-UiO-66(NH2)nanocomposites.Such a strategy can make the two ingredients undergo a relatively adequate interfacial interaction,leading to the efficient separation of photogenerated electron-hole pairs.As a result,the nanocomposites-exhibit enhanced photocatalytic activity compared with the pristine UiO-66(NH2).(5)A facile and general approach has been developed for the fabrication of highly dispersed Au,Pd and Pt nanoparticles on MIL-125(Ti)without using extra reducing and capping agents.Noble-metal NP formation is directed by an in situ redox reaction between the reductive MIL-125(Ti)with Ti3+ and oxidative metal salt precursors.The resulting composites function as efficient photocatalysts.