Preparation And Catalytic Performance Of Layered Double Hydroxides Pillared With Anionic Complexes

In this thesis anionic EDTA,oxalate,malonate,cyanide coordination compound of transition metal ions Ni²⁺,Cu²⁺,Co²⁺,Mn²⁺,Cr³⁺,are bridged through electrostatic and H-bonding interactions into Mg₃Al-LDHs and Ni₂Al-LDHs on the basis of the their anion exchange property.Mg₃Al-LDHs/[MY](M=Ni²⁺,Cu²⁺,Co²⁺,Mn²⁺,Cr³⁺, Y=EDTA),Ni₃Fe-LDH/[CoY]and Ni₃Al-LDH/[CoY]were synthsized by co-precipitation method.Intercalation compounds of Ni₂Al-LDHs,with[Cr(C₂O₄)₃]^3-, [Cr(C₃H₂O₄)₃]^3-,[Fe(C₂O₄)₃]^3- and[Fe(CN)₆]^3- complexes were obtained via intercalation and assembly processes.The composition,structure and property of the products thereby obtained have been studied by using XRD,FT-IR,ICP and TG-DTA. Catalytic activity for the H₂O₂ oxidation of cinnamaldehyde of the composite materials was also investigated.The results indicated that,all the obtained composites had better organized stacking arrangement by controlling experimental conditions:when the Mg/Al ratio was 3.00,co-precipitation was under pH=9.0,aging at 90℃24 h;when the Ni/Al ratio was 2.00,ion-exchange processes was under pH=6.5 and 85-90℃or ambient temperature for 48 h.XRD and vibrational spectroscopy studies confirmed that the integrity of the transition metal complexes was preserved upon incorporation into LDHs.TG analysis showed that all the composite materials obtained had well thermal stability,the layer structure was completely destoried above 400℃.The orientation and arrangement of the transition metal complexes within the interlayer had also been investigated.In the case of Mg₃Al- LDHs/[MY]the interlayer separation indicated that the guest species were arranged in a bilayer with the minimal dimension perpendicular to the host layers;In Ni₂Al-LDH/[Cr(C₂O₄)₃],Ni₂Al-LDH /[Cr(C₃H₂O₄)₃],Ni₂Al-LDH/[Fe(C₂O₄)₃],Ni₂Al-LDH/[Fe(CN)₆]the guest species were all arranged in a monolayer with their C3 axises perpendicular to the host layers.These orientations can maximize the electrostatic force and hydrogen bonds between the host and guest species.The host materials can meet the matching of volume,electricity and construction of the guest species,which were main factors in affecting the orientation and arrangement of the guest species.The catalytic activities of the composite materials were extensively studied.It was observed that the catalytic activities of the composite materials LDHs mainly attributed to the synergetic effect between transition metal complexes and LDHs.The most optimal catalytic performance came from the LDHs which the[CoY]^2- anion was intercalated into the interlayer space of Ni₃Fe-LDHs.