MOF-Derived Materials:Synthesis And Electrocatalytic Reduction Of Small Molecules

Metal-organic frameworks(MOFs),a class of crystalline porous materials built by metal ions/clusters and organic linkers,present many unique features,including crystalline nature,structural diversity,and tailorability as well as ultrahigh surface area and porosity.This enable them to be a highly versatile platform for potential applications in catalysis.Thanks to the superiority of MOFs,it can realise the accurate control over the composition of MOF-derived materials,and the porosity and long-range structural ordering of MOFs can also be partially preserved,which are also of vital importance for catalysis.Furthermore,the much enhanced stability of MOF derivatives makes them suitable catalysts for reactions under harsh reaction conditions.In this dissertation,a series of highly efficient MOF-derived electrocatalysts have been developed and used for the electrocatalytic reduction of small molecules.In addition,we have carried out detailed analysis of the catalyst structure by means of various characterization methods,and deeply explored the inherent structure-activity relationship and reaction mechanism,providing new ideas for the controllable design and synthesis of high-efficiency catalysts.The main contents of this dissertation are listed as follows:1.Combining graphene with MOFs to enhance the conductivity of MOF-derived materials.By using 2D graphene oxide(GO)as template,we have fabricated a MOF/GO sandwich-type composite with sheet-like structure based on the template role of GO via a facile one-step room-temperature reaction,without any bridging agent.Upon pyrolysis,the Co-based MOF/GO was converted porous CoP/rGO nanocomposite with retained sheet-like morphology.The resultant CoP/rGO exhibits excellent water splitting activity.At the same time,the structural evolution in the catalytic process is discussed in depth,which provides an important reference for understanding the structure-activity relationship of the catalyst.2.A new mixed-ligand strategy for the precise construction of single-atom catalysts was developed.Based on a porphyrin-based MOF(PCN-222)constructed by mixed ligands,the concentration and dispersibility of Fe atoms in the MOF framework were achieved by regulating the ratio of iron porphyrin ligands to non-metallated porphyrin ligands in MOF.As a result,the agglomeration of Fe atoms can be effectively inhibitted during pyrolysis.When served as electrocatalysts,FesA-N-C exhibits excellent ORR activity in both alkaline and acidic conditions,which is superior to commercial Pt/C.3.A new strategy for oxide assisted construction of high loading single-atom catalyst materials was proposed.On the basis of making full use of the structural advantages of MOFs,the oxides are introduced into the pores of MOFs.By means of the confinement of oxides to metal atoms,the migration and agglomeration of metal atoms during pyrolysis are effectively suppressed.Thus,the metal loading of single-atom catalysts can be significantly improved.As a result,the obtained single-atom Fe catalyst exhibits better oxygen reduction activity than Pt/C under acidic conditions.4.A universal synthesis strategy based on porphyrin-based multivariate MOF towards single-atom catalysts was developed,and a series of single-atom catalysts were constructed.The model system was used to deeply investigate the effect of metal species changes on carbon dioxide reduction activity.This provides an ideal model system for understanding the reaction mechanism of carbon dioxide reduction.