Construction Of MOF/Semiconductor Heterojunction And Its Photocatalytic Performance

Metal-Organic Frameworks(MOFs),also known as Porous Coordination Polymers(PCP),are a class of metal ions/clusters and organic ligands that are self-assembled by coordination bonds to form a periodic network-structured,porous solid crystalline material.Due to their special physicochemical properties such as high porosity,regular and adjustable pore structure and high specific surface area,MOFs have shown wide applications in selective gas adsorption separation,hydrogen storage,chemical sensing,heterogeneous catalysis and drug delivery.The secondary structural unit of MOFs are metal or metal-oxo cluster structure,which can exhibit semiconductor-like behavior.Therefore,in recent years,MOFs have attracted extensive attention in the field of photocatalysis.MOFs has unique advantages in the effective separation of photogenerated electron holes whrease the defects of wide band.Therefore,based on the synthesis of MOFs and W18O49 nanowires,two MOFs/semiconductor heterojunctions and their composites were designed and constructed for photocatalysis.The specific research contents are as follows:1)On the basis of the synthesis of Cd-MOF nanosheets,CdS/Cd-MOF binary heterostructure composites were prepared by in-situ sulfuration under mild conditions and applied to photocatalytic hydrogen production.Due to the unique heterojunction structure and efficient charge separation efficiency as well as transport characteristics,the composites have an excellent hydrogen production,up to 4927 ?mol-1g-l,which is 25 times than that of pure CdS nanoparticles.At the same time,it has superior stability and recyclability.After 20 h of reaction,the rate of hydrogen production did not decrease significantly.This method of constructing a two-dimensional sheet photocatalyst in situ opens up a new way for designing and synthesizing advanced 2D composite catalytic materials.2)Firstly,W18O49 nanowires with high aspect ratio were successfully prepared by solvothermal method.Then,the surface of W18O49 nanowires were modified by polyvinylpyrrolidone(PVP).And after that the metal organic framework Uio-66(NH2)with a size of about 20 nm uniformly grown on the surface of the nanowires and obtained a novel cane-like core-shell structured W18O49@Zr-MOF nanowires Moreover,by controlling the amount of metal ions,the thickness and gap length of the shell layer(Zr-MOF)can be adjusted.The heterojunction of W18O49@Zr-MOF can promote the separation of electrons and holes,synergistically,thus has strong enrichment and photocatalytic reduction properties for hexavalent Cr in water.The results of the catalytic performance show that the heterojunction structure of W18O49@Zr-MOF has a significantly improved photocatalytic reduction of Cr(VI)ability compared to the single component W18O49 nanowire and pure Zr-MOF.This novel core-shell structure also has potential applications in the fields of sewage treatment,energy storage,and drug delivery.