Synthesis,characterization And Catalytic Properties Of Fe-Mn And Zr-Co Mixed Metal MOFs

It is one of the challenges in the world for the synthesis of catalysts with good stability,high-efficiency,acceptable selectivity and environmentally-friendly.MOFs have been studied extensively in this area due to their diverse structures,definite compositions,large surface area and extensive catalytic active sites.Compared with traditional MOFs,mixed metal MOFs（MM-MOFs）are more and more popular as catalysts with good composition and synergistic effect.In consideration of the extremely high stability and the possibility of postsynthesis modification of Fe-or Zr-based MOFs,in thesis,we synthesised two MM-MOFs 1 and 2,named Fe Mn₂（BTB）（DEF）（OAc）₄and DUT-67（Zr）+Co,respectively,and studied their catalytic abilities in the oxidative coupling of mercaptan and photocatalytic reduction of CO₂.1.Aiming at the synthesis of Fe-Mn MM-MOF for the catalysis of oxidative coupling of mercaptan,Fe₂Mn（μ₃-O）（CH₃COO）₆（H₂O）₃cluster was obtained firstly,and then self-assembled with symmetrical H₃BTB.X-ray single crystal diffraction revealed that the obtained red cubic crystal 1 was formulated as Fe Mn₂（BTB）（DEF）（OAc）_4,where the Fe₂Mn core was decomposed and reconstructed as heterometallic chain;EDS and Mapping results indicated that the ratio of Mn to Fe is 2:1;TG and PXRD curves confirmed the high thermal and chemical stability of 1.Catalytic results showed that 1 exhibit excellent performance in the oxidative coupling of mercaptan,which can convert 4-methoxyphenthiophenol to Bis（4-methoxyphenyl）disulfide completely under air at room temperature with 99%selectivity.The high TON of 1353 h^-1is comparable to that announced.Meanwhile,1possessed wide substrates tolerance and good recycling ability.What’s more,control experiments revealed that the catalytic active site in is Mn²⁺while the Fe³⁺may contribute to the stability.2.Aiming at the synthesis of catalyst with excellent performance in the photocatalytic reduction of CO₂,DUT-67（Zr）with high structural stability and 8-connected cluster model was selected as the parent structure,after post metallization with Co²⁺,DUT-67（Zr）+Co（2）was obtained as expected.PXRD patterns showed that 2 maintain the structural stability of DUT-67（Zr）;XPS results,combining with the published models,indicated that Co²⁺exists in2 as the model of Co-O-Zr;EDS results revealed that the ratio of Zr to Co in 2 is about 2:1;UV Vis absorption spectrum and electrochemical results indicated that the introduction of Co²⁺broaden the absorption to visible area and improve the separation efficiency of Photocarriers.Photocatalytic results confirmed that 2 has superior performance to DUT-67（Zr）with the yield of HCOOH up to 237μmol g^-1h^-1,which is comparable to the reported data.This work has certain guiding significance for the synthesis of photocatalyst for photocatalytic reduction of CO₂.