Synthesis Of MOFs Composites And Its Characterization、Photocatalytic Performance Study

By tuning the solvent mixture,four CdII-based compounds,[Cd₃（BTB）₂（DMA）₄]·2DMA（1α）,[Cd₃（BTB）₂（DMA）4]·2DMA（1β）,[Cd₃（BTB）₂（DMF）₄]·2D MF（1γ）,Cd₂（BTB）（HCOO）（DMF）₃（2）have beensuccessfully separated from H₃BTB ligand and Cd（NO₃）₂ salts.Structural analyses revealed that compounds 1α,1βand 1γare iso-structural and have essentially identical local and two-dimensional structures constructed from trinuclear Cd₃（OCO）₆ unit.Their structural differences only arise from the different packing fashions,which are novel modes of supramolecular isomerism in coordination polymers.Compound 2 displays 3D two-fold interpenetrated network based on 1D infinite Cd₃(μ_1,1,3-OCO)₂（HCOO）chains containing mixed BTB^3-and formate ligands.The fluorescence measurements show that compounds 2 exhibit red-shifts（about 25 nm）in the solid state,compared with three iso-structural 1α,1βand 1γ,and this can be attributed to the cooperative effects of intraligandπ-π*transitions and ligand-to-metal charge transfer（LMCT）.In this work,we employed solvethermal method to assemble highly crystalline NH₂-MIL-125（Ti）nanocrystals on the CdS nanorods,forming CdS@NH₂-MIL-125（Ti）（S@T-n）heterostructured photocatalyst.The photocatalytic activity,structures and morphology of the composites were characterized by UV-vis diffuse reflectance,powder X-ray diffraction（PXRD）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,Brunauer–Emmett-Teller（BET）,photoluminescence（PL）,X-ray photoelectron spectroscopy（XPS）and electron-spin-resonance（ESR）.Compared to pristine CdS,the S@T-n composites exhibit enhanced photo-degradation efficiencies for Rhodamine B（RhB）,phenol and oxytetracycline（OTC）from aqueous solution under visible-light irradiation.Among them,the S@T-10 composite demonstrates the highest photocatalytic performance,and can reach 361.4 times for phenol,and 236 times for OTC of Degussa P-25.The enhancement of photocatalytic activity could be abscribed to the novel heterostructure,which can not only provide abundant surface area for the adsorption and diffusion of organic pollutants,but also efficient visible-light harvesting and interfacial charge separation.The possible photocatalytic mechanism of superoxide(O₂^·-)and holes（h⁺）by the ESR was also investigated detailed.