Water-Evaporation Induced Assembly Of Layered Coordination Polymers And Their Properties

Coordination polymers are a kind of porous solids,which have attracted interests because of their adjustable crystal structure and potential in applications such as catalysis,gas separation,sensing and so on.So far,the understanding of the properties of coordination polymer powders and single crystals has been developed well.However,the understanding about coordination polymer film and bulk structure,which is crucial for practical applications,but remains to be poor.The reason lies in the fact that most of the film growth and bulk forming of the coordination polymers rely on the modification of substrates or the addition of binders,therefore,lacking of simple ways to construct high purity and strong thin film and bulk structures.With reference to the excellent film forming and molding characteristics of clay,this thesis is dedicated to the self-assembly behavior of layered coordination polymer nanoparticles,expecting to obtain films and bulk structures with high purity and strength.This thesis selected a Hoffman-structured cyano coordination polymer nanoplates as the building blocks,observed the process of nanoplates assembly by water-induced evaporation,and examined the assembly rules of the nanoplates.The microstructure of the assembly was studied by means of electron microscope,X-ray microanalysis,gas adsorption and desorption analysis,and atomic force microscope,etc.The mechanical properties,mechanical behavior and structural functions of the assembly were evaluated by universal testing machine.The main research results are as follows:1.Coordination polymer thin films were deposited by stacking of coordination polymer nanoplates in a monoconfined and substrate-supported environment.Ni?H₂O?₂[Ni?CN?₄]·4H₂O?denoted as Ni-CN-Ni?coordination polymer nanoplates colloidal droplets were dropt to the glass substrate surface.By evaporation of water,the nanoplates were induced to be assembled on the surface of the substrate to form a dense film.Under the influence of ambient humidity and the concentration of nanoplates,the morphology of the deposited films switched between the ring and the disk.When the concentration of nanoplates and the ambient humidity were low,the Marangoni flow in the droplet drove the nanoplates to move to the edge,forming a ring film.When the concentration of nanoplates and the ambient humidity were high,the Marangoni flow was suppressed and the nanoplates were uniformly deposited to form a disk film.Van der Waals force and coordination effect between the nanoplates films and the glass substrate led to a strong bond.Therefore,the film could be further deposited on the surface of oxidized copper foil,and be folded for several times.2.In the double-sided confined space formed by stacking of the planar substrates,water evaporation induced the coordination polymer nanoplates to spontaneously stack between the substrates,resulting in the emergence of the adhesive ability,which glued the planar substrates together and became a new type of inorganic glue.When the concentration of the Ni-CN-Ni nanoplates was lower than 500 mg/mL,the colloidal viscosity was low and the fluidity was close to liquid.After evaporation of the water,the nanoparticles were stacked between the planar substrates and came into contact with the upper and lower planes.At the micro scale,the nanoplates were stacked together to form a lamellar structure.Van der Waals forces were existed between nanoplates.There were coordination effect and van der Waals forces between the nanoplates and the substrates.Collection of these microscopic forces resulted in the macroscopic adhesion effect,building the plane substrates strongly.Due to the non-covalent effect,adhesion was universal,and various materials could be firmly bonded by water-evaporation induced nanoplates assemblies.The shear strength of the bond was about 50 N/cm²,and the normal strength was about 9 N/cm².The uneven deposition caused by Marangoni flow could still be observed in the confined space.In order to overcome the uneven deposition,after increasing the concentration of Ni-CN-Ni nanoplates to 500mg/mL,the colloidal viscosity was significantly increased,presenting a slurry state.In the process of water evaporation,the Marangoni flow was inhibited.The film assembled by the nanoplates was evenly distributed between the substrates,expanding the total contact area between the nanoplates and the substrates.In this case,the adhesive strength of the nanoplates assembly was increased by 2-3 times.In the shear direction,the average strength reached about 190 N/cm².In the normal direction,the average bonding strength reached about 30 N/cm².3.In the environment with infinite space,Ni-CN-Ni nanoplates were processed into a green body.A high-strength bulk structure was obtained after water evaporation.When the concentration of the Ni-CN-Ni nanoplates exceeded 1000 mg/mL,the dispersion system further lost its fluidity.At this point,flow was inhibited,and the movement of the nanoplates became difficult.However,with the assistance of mechanical action?such as extrusion?,the nanoplates could be moved and twisted,stacking to form oriented domains within the block.The whole block was composed of domains with different orientations.The blank body shrinked into a block due to the shortening of the distance between the nanoplates.Among the domains,van der Waals forces were involved.Mechanical obstruction played a leading role.Under the effect of non-covalent and mechanical actions,the block had a certain mechanical stability,with a tensile strength to be about 60 N/cm²,and remained stable in the repeated gas and water adsorption.