The Preparation And Gas Separation Performance Of Metal Organic Framework Membrane

Compared with these traditional separation techniques such as distillation,adsorption,crystallization,and so on,membrane-based separation has received considerable attention due to energy efficiency,environmental protection as well as ease of processing and operation.The properties of membrane material play a key role in separation performance of membrane.Metal-organic frameworks?MOFs?have been considered as one of the most promising membrane materials due to well-defined pore structure,permanent porosity,tunable pore size and property.MOFs belong to the crystalline complex.The free-standing MOF membrane is not strong enough for subsequent application.Thus,various porous substrates have been used to support MOF membranes.To date,the research on fabrication of a continuous MOF film and its application in separation filed have been developed as one of the hot research topics.In this thesis,we have developed two preparation methods of MOF membrane:nanostructure array assisted aggregation-based growth and basic metal carbonate arrays self-conversion method.Corresponding results are described as follows:In the first part,we have reviewed the present preparation methods of MOF membrane and its applications in gas separation.The second part mainly includes the following two aspects:?1?We have developed a new preparation method of MOF membrane:nanostructure array assisted aggregation-based growth method,which was used to fabricate a continuous Co-MOF-74 membrane on Ni₃S₂ modified Ni foam substrate.It is found that the Ni₃S₂ nanostructure arrays can effectively improve the surface roughness of the substrate,provide attachment points for the initially formed Co-MOF-74 crystals,and allow them to grow into continuous membrane along the specific direction.The suitable reaction time for fabricating Co-MOF-74 membrane is defined between 6 and 12 hours.From the single gas permeation,it is found that the Knudsen diffusion is mainly dominant for H₂,N₂,CH₄,and CO₂.For the gas mixture separation,the resulting Co-MOF-74 membrane exhibits good H₂/CO₂ separation performances and stability,with the separation factor of H₂/CO₂ up to 8.5.?2?We have developed a universal preparation method of MOF membrane:basic metal carbonate nanoarrays self-conversion method.Here we demonstrate that basic metal carbonate nanoarrays as the unique metal source modified on the porous metal foam substrate can react directly with organic ligands and lead to the in situ growth of continuous MOF membranes.This method can markedly increase the adhesion between substrate and MOF film,simplify the process of membrane making,and provide a new idea for the preparation of MOF film.Due to the universality of this method,we have developed Cu₂?OH?₂CO₃ as the unique metal source for preparation Cu-based MOF membranes:HKUST-1,CuBDC,and MOF-110,as well as CoOH?CO₃?_0.5 as the unique metal source for preparation of Co₃?HCOO?₆ membrane.We have studied the influence factors of the preparation of HKUST-1 film in details and the gas permeability of the obtained membrane.The results show that the suitable preparation condition of HKUST-1 membrane is that the suitable solvent is water/ethanol?1:1 v/v%?,the optimum ligand concentration is 25 mM,the formation time is not less than 2 h.And it is found that the Knudsen diffusion is mainly dominant for light gases in the prepared membrane.