Preparation And Properties Of Metal-organic Framework Compounds And Their Derivatives Based On Microfluidics

Metal organic frameworks（MOFs）compounds are a new class of porous materials with large specific surface area,richly tunable pore channels,many active metal sites,and diverse topologies,which have been widely used in recent years in the fields of non-homogeneous catalysis,fluorescence sensing,adsorption and separation,and drug transport and therapy.In order to meet the needs of MOFs development,researchers have developed various synthetic means such as wet chemistry,solvent/hydrothermal,and electrochemistry.However,despite the abundance of methods for the preparation of MOFs,most of them are intermittent reactions with the following limitations:1.long production cycle and low preparation efficiency;2.the morphology of the prepared MOFs are nanoparticles,which are not conducive to morphology control and functionalization modification;3.the reaction process is confined and cannot be observed in real time.Therefore,it is of great research value and significance to develop a method with high visualization,continuous adjustment of the reaction process and high efficiency in the preparation of MOFs materials.Microfluidic synthesis is a laboratory preparation technology that has emerged in recent years.This kind of method has continuous reaction process,high mass transfer and heat transfer efficiency;the reaction ratio and time can be precisely controlled;the reaction can be detected in real time,which is conducive to the study of material formation mechanism.Therefore,we used the microfluidic technology to synthesis the lanthanide metal-organic framework microspheres,and studied its formation process;According to the characteristics of the microsphere superstructure,we prepared multifunctional MOFs composites using microchannel devices and synthesized bimetallic Zn Co-ZIF materials in high throughput and studied their derivatives in the application of oxidase-like enzymes.The details are as follows:1.Lanthanide fluorescent MOFs materials with microsphere structure were prepared by single-channel glass capillary droplet microfluidic chip.It is shown that the MOFs polycrystalline microspheres are solid structures composed of single-crystal nanorods of Ln-BTC-6H₂O（Ln stands for lanthanide ions）,and the nanorods on the surface of the microspheres are neatly arranged and oriented in an orderly manner,showing a super structure.The formation of solid structure is due to the transient deformation of MOFs microspheres during dynamic growth and the non-densified pores at the pre-crystal forming stage,which allow the reactants to enter the interior.The size of the microspheres can be adjusted by the flow rate and the diameters are in the range of 110-327μm.In addition,the fluorescence emission wavelength of the MOFs microspheres can be tuned from blue to red by changing the metal ions of the reactants.2.Based on the microfluidic preparation of MOFs microspheres,we prepared Iron oxide@MOF and Glucose oxidase@MOF composites with magnetic and enzymatic catalytic activities,respectively,by adding functional materials to the internal phase;MOF@Tetraphenylene and MOF@Rhodamine-B composites with excellent optical properties were prepared by impregnating the microsphere surface with modification.In focus,we investigated the preparation of MOF@Perovskite quantum dots（PQDs）and their fluorescence properties,and by regulating the concentration of PQD colloid,we achieved different loading rate PQD loading on MOF microspheres.Further,the composites were applied to humidity detection,which exhibited ratiometric fluorescence sensing performance.3.A synthetic system of flow chemistry was constructed based on a microchannel reactor for the continuous controlled bimetallic Zn Co-ZIF（Zeolitic Imidazolate Frameworks）.Compared with the conventional method,the basic properties of the products were similar,but the microfluidic synthesis yield and space time yield conversion were as high as 61.6%and184 kg·m^-3·d^-1,respectively,which were much larger than traditional methods.Further,the samples prepared by microfluidic were pyrolyzed at 900°C to N-doped carbon materials containing Co nanoparticles,which showed excellent oxidase-like activity.The maximum reaction rate was 4.19×10^-7 Ms^-1 with a Michaelis constant of 0.12 m M.The nanozyme could detect ascorbic acid at 0-500μM with a detection limit of 17.87μM.