Proton Conduction And Adsorption Properties Of Metal Organic Framework Materials Constructed By Ploycarboxylate Ligands Containing Pyridine

Metal-Organic Frameworks（MOFs）are novel functional materials developed in the past two decades.Compared to traditional materials,MOFs are widely used in various fields and are considered to be one of the most exciting materials today due to its unparalleled designability and functionality.The use of ligands containing functional sites to construct novel MOFs is beneficial to improve the performance of materials,which is crucial for the application and development of MOFs.In this paper,we selected the ligand of polycarboxylic acid ligands containing pyridine sites to construct a series of different functional MOFs materials,and explored their distinct properties for their structural characteristics.Firstly,by controlling the degree of interpenetration of the framework,we first regulate the proton conductivity of two In-MOFs.The 2-foldinterpenetrated FJU-17exhibits higher intrinsic proton conductivity and wider performing temperature range than the 4-fold interpenetrated FJU-16.The intrinsic proton conductivity of FJU-17 is1.08×10^-2 S/cm at 100°C without additional humidity,which is the highest reported under the same conditions.We can effectively control the proton conductivity of MOFs by reasonably designing the degree of interpenetrationof framework.In order to further enhance the proton conductivity of MOFs,the dye molecule8-hydroxy-1,3,6-methylenetrisulfonic acid trisodium salt（HPTS）was added the growth solution of MOF by one-pot method,but during the reaction,HPTS was nitrated andnitrated HPTS was encapsulated into the FJU-10 to obtain dye@FJU-10.Compared with the mother FJU-10,the intrinsic proton conductivity of dye@FJU-10 is increased by five times.And it also showed higher the sensitivities of detecting aniline in dye@FJU-10.Here,it is firstly demonstrated that the proton conductivity can be effectively improved by encapsulating a nitrated HPTS dye into the MOFs.Considering that the pyridine nitrogen can act as a Lewis base site to enhance the gas adsorption capacity.We obtain two structurally isomeric Cd-MOFs,FJU-35 and FJU-36 containing different Cd^II-O-Cd^II chains by varying the addition agents.Due to the difference in the Cd^II-O-Cd^II chains,the stability of MOFs is different.The FJU-36exhibits high stability,and there are open pyridine nitrogen decorating the channel.After activation,FJU-36a exhibits high the uptake capacity of C₂H₂,and the dynamic breakthrough experiment further demonstrate that the stable FJU-36a exhibits a high C₂H₂ selectivity over CO₂ and CH₄,while unstable FJU-35a demonstrates almost no gas adsorption capacity.Conversely,FJU-35 with more vulnerability is more sensitive to the detection of nitrobenzene than FJU-36.We demonstrate that regulating the metal-O-metal chains can enhance stability,gas adsorption,and sensing of MOF materials.To generate multivariate MOFs that are diversity and modular,there are still great challenges.We introduce the multicluster and the multicomponents into MOF（MM-MOF）and define them as different cluster and mixed ligand within a MOF to generate complexity unaltered the topology.Combining Hina（Hina=isonicotinic acid）,H₂BDC（H₂BDC=1,4-phthalic acid）and H₃BTB（H₃BTB=benzene-1,3,5-tribenzoic acid）and Co^III produces a MOF,FJU-6 with the different clusters.The FJU-6 is intricate（3,9,12）connected topology LLZ.Based on FJU-6,eight different BET of MM-MOFs were obtained by changing the different ligands and metals without changing the framework.When the pyridine nitrogen sites of the ligand were regulated,the BET and the adsorption amount of CO₂ and C₂H₂ increased with the increase of the pyridine nitrogen site.This work not only increases the diversity of MOFs but also improves the performance of MOFs and further provides an idea for designing multivariable MOFs.