| Semi-rigid polycarboxylate aryl ether ligand with the characteristics of rigidity and flexibility,which are favorable to the construction of metal-organic frameworks(MOFs),due to their multiple coordination sites,strong coordination ability and flexible conformation.The potential applications of MOFs based on semi-rigid polycarboxylate aryl ether ligand in topological regulation,host-guest adsorption,photoelectric catalysis and other fields have aroused researchers’ interest.In this paper,a series of MOFs were designed and synthesized by self-assembly of transition metals and 3,5-bis(3,5-dicarboxylate phenoxy)benzoic acid(H5L),which has rich π-electrons and multiple carboxylic acid functional groups.The synthesis,structure and properties of MOFs were studied and discussed in detail.Specific research contents are as follows:1.Based on the semi-rigid characteristics of ligands,four MOFs:{[Zn9(L)2HL)2(H2O)10]·9H2O}n(Zn-L1),{[Zn3(μ3-OH)(L)(H2O)3.5]H2O}n(Zn-L2),{[Zn2(HL)(H2O)2]·4H2O}n(Zn-L3)and {[Zn5(L)2(H2O)5]·16H2O}n(Zn-L4),with distinct Zn-O cluster second building units(SBUs)were directly constructed by adjusting the ratio of mixed solvents.Then the nucleus number of Zn-O clusters were regulated by combining with post-modification structural transformation.The results showed that the solvents had a significant effect on the self-assembly process.In different solvents,the ligand underwent different torsion changes in order to adapt to different environments.resulting in the change of SBUs.2.Based on the 7r-rich electron characteristics of the ligands,three MOFs:{[Zn3(μ3OH)(L)(H2O)3]·2H2O}n(Zn-L6),{[Zn3(μ3-OH)(L)(H2O)]·2DMF·3H2O}n(Zn-L7).and｛[Zn3(μ3-OH)(L)(DMF)2]·H2O}n(Zn-L8).with different channel sizes,potential sites for charge-transfer interaction and halogen bonding,were synthesized.The effects that porosity and arrangement of weak interaction sites of MOFs hosts on the iodine uptake performance were validated.Among them.Zn-L7.with a medium channel size and suitable arrangement of noncovalent interaction sites,exhibited higher I2 adsorption capacity than two other MOFs.3.Bioinspired by the carboxylate-water hydrogen bond networks around the Mn4Ca-oxo water splitting center in photo system Ⅱ.the hydrogen bonds riched monometallic{[Co2(HL)(H2O)5]·3H2O}n(Co-HL).{[Ni2(HL)(H2O)5]·3H2O}n(Ni-HL)and bimetallic Co/Ni-HL(x:y)with different Co/Ni ratios were obtained based on the polycarboxylic acid characteristics of the ligand.The carboxylate-water hydrogen bond networks around the transition-metal sites contributes to electron injection and the synergistic bimetallic effect to support electrochemical applications.Among them.Co/Ni-HL(5:5)exhibited the optimal water splitting performance.Then,this bimetallic MOF was grown in situ on FeNi foam to improve the conductivity,and the composite material Co/Ni-HL(5:5)@FeNi foam exhibited excellent performance,with overpotentials of 258 mV vs RHE for the OER and 90 mV vs RHE for the HER at 10 mA·cm-2,a voltage of 1.52 V vs RHE for overall water splitting;its performance was comparable to that of electrocatalytic materials based on precious metal.4.Inspired by the close configuration between the proton and electron transfer pathways found in iron hydrogenase,we use Ni-HL with hydrogen-bond clusters as catalyst and dye fluorescent(FL)as a photosensitizer,to construct the photocatalytic water decomposition system of MOF Ni-HL and FL.By introducing the dye FL into the hydrogen bond network,the photogenic electron transfer pathway and proton transfer channel in the dye FL sensitized MOF were combined effectively.Under visible light irradiation,efficient hydrogen production can be achieved,showing potential application in the field of photocatalytic water decomposition.The research content of this paper will provide knowledge reserve for the realization of the intrinsic advantages of coordination porous materials such as MOFs on their further applications in structure control,host-guest behavior,optoelectronic devices and catalysis. |
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