Mass Transfer Property Of Sub-nanometer Channels Based On Metal Organic Frameworks

Nanopore includes pore or channel structures with their pore size in nanoscale.The interaction between nanopore and analyte molecule cannot be ignored when considering mass transfer through these pores because of their similar size.New signal output that different from the signal obtained from macroscale experiments are expected,which may contributes to applications including DNA sensing,bionic sensor and drug delivery.Zeolitic Imidazolate Framework(ZIF)is a sub-class of Metal Organic Framework(MOF)formed by the coordination of metal ions with organic ligands displaying sub-nanometer sized porous structure.Similar with zeolite,ZIF exhibits bigger surface area,adsorptive property and adjustability.As one kind of ZIF structure,ZIF-90,could be synthesized in aqueous phase under moderate conditions with a pore aperture of 0.35 nm(six-membered ring)which are orderly arranged into sub-nanometer channel array.The sub-nanometer pores in ZIF-90 has similar size with regular ions,therefore,the interaction between ions and the pores determines the ion transfer behavior.Understanding factors that affect the ionic current are fundamentally important for studying mass transfer through sub-nanopores.This paper prepared sub-nanometer pores based on ZIF-90 using glass nanopipette(orifice about 200 nm)as a supporting platform.This Glass-Nanopipette-Supported ZIF-90(GNS-ZIF-90)was used for the research of ionic transfer in water for its close size to ions and the paper includes four chapters:Chapter 1 introduces the development of nanopore analysis,nanopore materials and MOF materials.It also indicates the great innovativeness and potential application of MOF as nanopore materials.Chapter 2 introduces the preparation of GNS-ZIF-90 and characterization of ZIF sub-nanometer nanochannels.Chapter 3 researches the asymmetric ionic transfer in GNS-ZIF-90 and the relationship between ionic rectification and solution’s pH.The mechanism is also proposed to explain the results.Chapter 4 researches the performance of GNS-ZIF-90 in situations of big-sized cations,gas absorption and potential jump.Results confirm the mechanism above and indicate the application of ZIF nanochannels.