Synthetic Design And Application Study Of Novel Metal-organic Framework Nanostructures

Metal-organic frameworks(MOFs)are crystalline coordination networks constructed with inorganic nodes and organic linkers with two or more ligation sites.Though some were reported before 1990,the real milestone is the discovery of MOF-5 by Yaghi et al.in 1999.Due to the unique framework structure,MOFs enjoy an obvious advantage as microporous materi als in gas adsorption and storage,receiving tremendous attention in recent years.Since then,the field is burgeoning,with the structural and functional varieties being investigated and explored in depth.Traditional studies are focusing on the design of new MOFs and characterizations of the new MOF crystals.Through designing the geographic combinations of inorganic nodes and organic linkers,more than 20000 new MOFs have been reported so far.Except for the traditional studies in coordination chemistry,the introduction of interdiscipline adds fresh blood.With the development of nano MOFs,we can understand the MOF framework better,especially the bonding and surface properties,and tune structures more accurately in a smaller scale.Therefore,we have developed several novel MOF nanostructures,exploring more synthetic possibilities.MOFs usually have micropores,which in turn limit fast mass diffusion and restrain larger molecules from entering into the center through their micropores,hence restricting the potential practical applications in some cases.If we introduce mesopores into the previous microporous MOF structures,the as-achieved hierarchical-pore MOFs(H-MOFs)would combine both benefits and be advantageous in complete utilization of materials.The micropores provide exceptionally high surface areas and large pore volumes,whereas the mesopores facilitate diffusion and accessibility.However,there are merely a few effective synthetic methods,which require either a template or complicated techniques,and are difficult to extend to other systems.So new versatile methods are imperative to establish stable and high-quality H-MOFs.Herein,we developed a competitive coordination strategy for synthesis of H-MOF nanostructures.This strategy is effective in several MOF systems,achieving two-dimensional porous nanosheets and three-dimensional porous nanocubes.Furthermore,the as-achieved H-MOF nanosheets can serve as a substrate to in situ immobilize Pd nanoparticles without any surfactant,using a simple soaking method.The new Pd catalyst exhibits excellent catalytic performance.