Based On [In(COO)₄] Cluster Controllable Design Of Anionic MOFs And Application Research On The Electrical Properties Of Their Skeletons

Anionic MOFs refer to the porous metal organic frameworks with negative charge.Usually,the cations embedded in the pore of MOFs can balance the framework charge of and thus maintain the overall electrical neutrality of the material.Thanks to the framework charge and the exchangeability of cations,anionic MOFs exhibit excellent performance in greenhouse gas capture,ion exchange,organic dye adsorption and separation,and so onHowever,the preparation of MOF materials still relies on a large number of random trial experiments up to now.The controllable synthesis of MOFs is still a challenging task.Based on the[In(COO)4]monuclear cluster with one negative charge and the polycarboxylate ligands(H3L4,H4L4,H4L4A,H5L5 and H6L6)with different geometric shapes,this thesis successfully achieved the controllable synthesis of anionic MOFs(SNNU-82-87).Furthermore,the selective adsorption ability of these anionic MOFs to organic dyes and their electrochemical properties as cathode materials for lithium ion batteries were systematically investigatedSingle crystal structure analysis showed that SNNU-82-87 compounds all were anionic MOFs formed by[In(COO)4]mononuclear tetrahedral clusters and polycarboxylate linkers.In all structures,mononuclear clusters serve as 4-connected nodes,while polycarboxylate ligands serve as 3-,4-,5-and 6-connected nodes to form a series(4,n)-connected binodal topological skeleton.The organic amine cations are embedded in the pores to balance the negative framework charge.The Zeta potential values of SNNU-82-87 were-36.1,-43.2,-44.0,-30.7,-37.9 and-31.3 mV,which further proved the electronegativity of these MOFsCationic methylene blue(MB),anionic methyl orange(MO)and neutral Sudan I were selected as three dye models to evaluate the dye adsorption performance of anionic MOFs.As a result,only cationic MB was selectively adsorped,which futher proved the framework electronegativity of these MOFs.Based on the adsorption kinetics,thermodynamics and isothermal model for MB adsorption,SNNU-82,-83,-85 and-87 MOFs all obey the quasi-second-order kinetic model.SNNU-82,-85 and-87 MOFs obey the Freundlich adsorption isothermal model,belonging to multi-layer adsorption,while SNNU-83 obeys the Langmuir adsorption isothermal model,belonging to single-layer adsorption.Moreover,the MB adsorption of SNNU-82,-85 and-87 belongs to the endothermic reaction process that can be spontaneous and the disorder degree increases,while SNNU-83 belongs to the exothermic reaction process that can be spontaneous and the disorder degree decreasesThe application of SNNU-85,-86 and-87 MOF materials in lithium ion batteries was discussed based on their framework electrical properties.After the Li+exchange,all three anionic MOF materials have good cyclic stability,excellent electrochemical reversibility and structural stability as the cathode materials for lithium ion batteries.At the current density of 20 mA/g,SNNU-85 and-87 have extremely high charge-discharge specific capacity.After 100 cycles of charging and discharging,they can still reach 120 mAh/g,which is higher than most of the porous materials reported so far.