Upscale Synthesis And Property Of Flexible Tetrahedral Imidazole Framework

Metal-organic frameworks(MOFs)have attracted much attention due to their various structures,adjustable pore sizes and easily functionalized surfaces.Among them,flexible metal-organic framework(flexible MOFs)can respond to external stimuli(guest molecules,light,heat,electricity,etc.)while maintaining its own crystallinity,showing interesting stimulus response performance.It is of great significance in the fields of gas adsorption and separation,specific recognition of guest molecules,proton conduction,catalysis and fluorescence.In 2011,our research group reported a tetrahedral imidazole frameworks(TIFs)material.TIF-A1 is a 3D framework with 1D rhombic channels.It's composed of Zn salt,adenine and isonicotinic acid.The framework contains a large number of unsaturated nitrogen sites and amino groups,showing good adsorption and separation performance for carbon dioxide.TIF-A1 containing amide guest molecules of different sizes showed a certain degree of flexibility.After removing the guest,the framework uniformly showed the characteristics of rigidity.In this paper,TIF-A1 was used as the research object to explore different synthesis methods,select different gas molecules as probes to detect its flexible characteristics,and further study its bactericidal performance.Firstly,we developed the facile methods for fast and upscale syntheses of TIF-A1.A variety of facile methods(room temperature,ultrasonic,stirring,reflux)were developed to realize the rapid synthesis of TIF-A1 by improving the original traditional solvothermal method from the factors of reaction materials,synthesis conditions and products.Upscale synthesis of TIF-A1 can be achieved by direct heating(>800 g),the obtained product has good crystallinity and acid-base stability.The excellent gas separation performance of TIF-A1 was further confirmed by single component gas adsorption and binary components breakthrough experiments.Based on a large number of TIF-A1 materials obtained by facile methods,we studied the flexibility of TIF-A1 using acetylene as probe molecule.In the previous work,TIF-A1 showed the characteristics of rigidity for nitrogen,hydrogen,carbon dioxide and other small molecule gases.Furthermore,TIF-A1 exhibits temperature dependent flexible adsorption properties for acetylene when C2 alkanes are used as probe molecules.The structure of TIF-A1 was characterized by in situ single crystal,synchronous X-ray diffraction and molecular simulation.The dynamic change of the structure was mainly attributed to the strong interaction between the acetylene molecule and the frame,which promoted the rotation of the isonicotinic acid ligand.By introducing amino to construct an isostructural NH₂-TIF-A1 framework,it is found that the introduction of NH₂makes acetylene unable to get close to isonicotinic acid and induce the flexibility of the framework.Similarly,the residual guest molecules in the pore also weaken the interaction between acetylene and the frame.Flexibility is an inherent property of TIF-A1.The change of TIF-A1 sample size or defects(p H treatment)will not affect its flexibility.Considering that TIF-A1 is composed of Zn ions,adenine and isonicotinic acid with low biological toxicity,we studied its bactericidal performance with Escherichia Coli(E.coli)and Staphylococcus aureus(S.aureus)as strains.The antibacterial activity of TIF-A1 was studied by incubation time and the dosage of TIF-A1.The results showed that TIF-A1 had good antibacterial effect on both bacteria.We speculate that the possible mechanism is that TIF-A1 can release Zn ions and adenine as active carrier,which has certain antibacterial effect on E.coli and S.aureus.Because the experiment is still in the early stage of exploration,we will further study its antibacterial mechanism in the follow-up work.