Study On The Design Of Novel Transition Metal-based MOFs Materials And Their Catalytic Performance

With the rapid progress of modern industry and agriculture,energy consumption seriously threatens the survival development and ecological balance of human beings.Therefore,the exploration of new economic and environmental protection catalysts has attracted great attention.Since their discovery in the 1990s,MOFs have been a hot research topic in many disciplines and have made explosive progress.with high specific surface area,a large number of uniformly distributed active sites,unique tunable structures and both inorganic materials,MOFs materials have been widely used in chemical,environmental and energy-related fields.At the same time,it is used as an electrocatalyst material with disadvantages that affect the catalytic effect.Firstly,MOFs materials are less stable in water and acid-base,easy to dissolve and difficult to recover,which is not conducive to electrocatalytic performance testing;secondly,MOFs materials have poor electrical conductivity and weak electrochemical response,which hinders electron transfer;furthermore,most MOFs materials have few active sites,and the performance can be improved by constructing heterogeneous systems.Therefore,we need to design suitable and novel MOFs materials with good stability and improve the conductivity to improve the solution of catalyst materials for photocatalytic,electrocatalytic and fuel cell applications.The main research is as follows:Part I:Firstly,the characteristics of MOFs materials are introduced by reviewing relevant literature;Secondly,the progress of MOFs materials in photocatalytic degradation,proton conduction,methanol oxidation and urea oxidation,and the progress of oxidation applications are discussed,and the advantages and disadvantages of MOFs materials in photocatalysis and electrocatalysis as well as the improvement measures are elaborated to accumulate experience for the design and construction of subsequent materials;Finally,the rationale for the selection of this paper and the research direction are described.Part II:In this chapter,four carboxylic acid ligands(2,5-dihydroxyterephthalic acid(H4DOBDC)and 2,5-dimercapto terephthalic acid(H4DSBDC),monosodium salt of 5-thioisophthalic acid(SIP)and monosodium salt of 2-sulfoisophthalic acid(STP))were selected as the main ligands,and short-chain nitrogen-containing co-ligands with metal ions of Mn,Cu,Ni and Co were introduced by the solvothermal method to construct Ten MOFs materials were constructed.The crystal structures and the related basic structural characterization were discussed with emphasis on the 10 novel transition metal-based MOFs materials as follows:{[Co(DOBDC)(bip)]}n(1){[Ni(DOBDC)(bip)]}n(2){[Mn(DOBDC)(bip)]}n(3){[Co2(?2-OH)2(DSBDC)]}n(4){[Cu2(?2-OH)2(DSBDC)(bpe)]}n(5){[Cu2(?2-OH)(SIP)(1,4'-bib)2]}n(6){[Cu2(SIP)(4,4'-bibp)2(HCOO)]·3H2O]}n(7){[Co2(SIP)(4,4'-bibp)2(HCOO)]·3H2O]}n(8){[Cus(?3-OH)5(STP)2(4,4'-biby)2(H2O)2]·4H2O]}n(9){[Co2(?2-OH)(STP)(bpe)2]}n(10)Part ?:Three new Cu(?)coordination complexes(Crystalline materials 6,7 and 9)consisting of sulfonic acid-based functionalized benzodicarboxylic acids and different nitrogen-containing co-ligands have been successfully synthesized and characterized.The results show that the three different structurally characterized sulfonic acid-based functionalized Cu(?)compounds possess different photocatalytic activities and proton conductivity.The photocatalytic decomposition rates of RhB under visible light were 98.1%for CTGU-20(Crystalline material 9),94.6%for CTGU-21(Crystalline material 6)and 96.2%for CTGU-22(Crystalline material 7),respectively;The photocatalytic decomposition rates of MB were 97.6%for CTGU-20(Crystalline material 9),94.6%for CTGU-21(Crystalline material 6)and 96.6%for CTGU-22(Crystalline material 7),respectively;The photocatalytic decomposition rates of BPEA were 98.8%for CTGU-20(Crystalline material 9),96.2%for CTGU-21(Crystalline material 6)and 98.3%for CTGU-22(Crystalline material 7),respectively.The number of degradation of RhB,MB and BPEA dyes by the three complexes was significantly higher compared to the control experiments.During photoexcitation,the charge may be transferred from the highest occupied molecular orbital of the O or N atom to the lowest unoccupied molecular orbital of the Cu(?)ion.To counteract this imbalance,the highest occupied molecular orbital strongly requires the electron to return to the steady state.Therefore,capturing electrons in water molecules can degrade organic dyes and enable photocatalytic processes.Meanwhile the unique pore structure of Cu-MOF provides a large number of exposed active sites for photocatalytic degradation.The proton conductivity(?)of the ligands CTGU-20(Crystalline material 9),CTGU-21(Crystalline material 6)and CTGU-22(Crystalline material 7)reached maximum values of 2.86 × 10-4 S·cm-1,1.58 × 10-5 S·cm-1 and 4.58 × 10-5 S·cm-1,respectively.The ? values of CTGU-20(Crystalline material 9)are much higher than those of MIL-53 with 1,4-benzenedicarboxylic acid ligand(3.6 × 10-7 S·cm-1 at 80?@95%RH).The higher proton conductivity of CTGU-20(Crystalline material 9)at certain humidity can be attributed to the incompatible hydrophilic sulfonic acid groups on the pore wall of CTGU-20(Crystalline material 9)and the The hydrogen bonding synergy between the coordinated hydrophilic sulfonic acid groups and the lattice water molecules on the pore surface contributes to the enrichment of ambient water molecules into the pores and accelerates the proton transfer.Meanwhile,the hydrophilic pores functionalized by a large number of-SO3 sites in CTGU-20(Crystalline material 9)can trap water molecules and form a fast and convenient proton transfer pathway.This work not only provides new coordination polymers for unexplored sulfuric acid functionalized aromatic carboxylic acid ligands,but also provides new ideas for the design of bifunctional Cu(II)-based photocatalytic and proton-conductive materials.Part IV:An example of Ni-MOF(Crystalline material 2)with stable and clear chemical environment and high material utilization was selected and used as a bifunctional catalyst material for MOR and UOR.Ni-MOF has a three-dimensional porous multiple interspersed structure with certain catalytic properties.After performance tests,it was found that the Ni-MOF material responded well in methanol and urea,and its area activity/mass activity in methanol was 13.08 mA cm-2/230.8 mA mg-1,showing a clear redox peak pair.In order to further improve the catalytic performance of the material,which has to be improved compared to inorganic materials,Ni-MOF was assembled with heteroparticulate nanomaterials.When the heteroparticulate nanomaterials were introduced,it led to a qualitative leap in the electrical conductivity,catalytic activity,and stability of the materials,which in turn accelerated the electron transport and thus improved the catalytic performance.The Ni-MOF@Fe3O4/NiOOH(3:1)catalyst material,which exhibited higher catalytic activity and durability in alkaline solution,showed an area activity/mass activity of 48.15 mA cm-2/849.5 mA mg·1 in 1 mol L-1 methanol,which was 3.68 times higher than that of Ni-MOF;in 1 mol L-1 urea,its area activity/mass activity was 87.11 mA cm-2/769 mA mg-1,which was 3.53/3.44 times that of Ni-MOF,and it exceeded most of the reported non-precious metal catalysts.The complexes and catalytic centers were derived by PXRD,FT-IR,TEM,and XPS analyses,and the synergistic effect between the two was enhanced by the introduction of Fe3O4/NiOOH heteroparticulate nanomaterials,,which improved the conductivity of the catalysts thus promoting the ability to catalyze.The key to the formation of Ni-MOF@Fe3O4/NiOOH nanostructures is that under solvent heat treatment conditions,from the complex,the metal can be decomposed in the order of Ni and Fe,and the potential NiOOH promotes MOR and UOR activities through the exchange stabilization of reactive oxygen species.This research strategy provides a new perspective for the construction of MOF semi-derivative MOR and UOR catalysts,which will enrich the research scope of MOF and its derivative materials and help to explore more efficient electrocatalysts.