Design And Application Of Nanofluidic System Based On Biomimetic Covalent Organic Framework Membranes

Nanofluidics is generally defined as the study of fluid motion through or past structures with a size in one or more dimensions in the 0-100 nm range.There are lots of unique phenomena in nanopores or nanochannels.The critical principles can be briefly introduced,namely physical factors of size,shape,and charge(Debye layer)and chemical factors of wettability,host-guest recognition,and other interactions.Among these factors,electrical double layer(EDL)has become the focus because of its wide application and remarkable effects.This paper focuses on the research of bionic artificial nanopores.In the first chapter,the concept of nanofluid and the nanofluidic phenomena in animals are introduced.Then we summarize the mechanism of ionic nanochannel and the development of osmotic energy harvesting,bionic thermosensation,and covalent organic frameworks(COFs)membranes.Therefore,designing biomimetic covalent organic framework-based nanofluidic membranes is practicable.In the second chapter,we summarize materials,equipment,and the methods of fabrication and experiment.Then a COF synthesized by the condensation of 1,3,5-triformylphloroglucinol(Tp)and triaminoguanidine hydrochloride(Tag)was chosen for the construction of nanofluidic systems,including osmotic energy harvesting and bionic thermosensation.In the third chapter,we introduce a reverse electrodialysis(RED)system,generating power from salinity gradient energy.TpTag-COF/PAN has high density of charged sites and the smallest pores among the 2D COFs reported to date.The high density of the charged sites present in the sub-nanochannels renders superior permselectivity to the resulting nanofluidic system.Then the changes of open circuit potential,short-circuit current,and permselectivity under different concentration gradients are described.Additionally,we also find K+is electrostatically accumulated near the negatively charged channels whereas Cl-is depleted.Significantly,by connecting twelve tandem TpTag-COF/PAN stacks,the output voltage can power electronic devices.These findings provide insights to construct cascading nanofluidic systems based on COFs for energy harvesting.In the fourth chapter,we report a nanofluidic membrane based on an ionic covalent organic framework that is capable of intelligently monitoring temperature variations and expressing it in the form of continuous potential differences.The potential applicability of the developed system is illustrated by its excellent tolerance toward a broad range of salt concentrations,wide working temperatures,synchronous response to temperature stimulation,and long-term ultrastability.Therefore,our study pioneers a way to explore COFs for mimicking the sophisticated signaling system observed in the nature.