Fabrication And Catalytic Application About Metal Clusters Confined In Porous Organic Materials

Metal cluster catalysts with ultra-fine size and uniform dispersion,which can effectively catalyze specific reactions are of high economic value.However,metal cluster is easier to agglomerate,which greatly affects the activity and stability of the catalyst,due to the quantum size effect.Therefore,it has become a hot topic in the field of catalysis that how to construct a metal cluster catalyst with high activity and stability.In this paper,the metal clusters catalysts were successfully fabricated by constructing porous organic cages and porous organic polymers with multi-level pore structure and high specific surface area.It was confirmed that the metal clusters were uniformly dispersed on the support material,and the particle size was all less than 2 nm,which greatly improved the catalytic activity of the catalyst,through a series of characterization and catalytic experiments.The anchoring group and multi-stage pore structure in the support material make the metal clusters firmly fixed in the support material,thus greatly improving the stability of the catalyst.The specific research contents of this paper are as follows:(1)The CC3-R porous organic cage support material with high specific surface area and micropore-mesoporous structure was prepared by the condensation reaction of1,3,5-benzenetricarboxylate and 1,2-diaminocyclohexane.The impregnation-reduction method was used to encapsulate the Ru clusters into organic cages to obtain the Ru@CC3-R metal cluster catalyst with smaller size,more uniform dispersion,higher activity and stronger stability.Compared with other Ru-based catalysts,Ru@CC3-R catalyst showed higher catalytic activity and stability in the hydrolysis of ammonia borane and tandem hydrogenation reaction of nitrobenzene.The problem of metal cluster instability is solved.It provides an effective method to fabricate stable metal cluster catalyst for the efficient catalytic hydrolysis of ammonia borane.(2)Based on the development concept of green and environmental protection,hydrogen was used as the hydrogen source to reduce nitrobenzene in water under mild conditions.In this work,Pd@3D-HPOPs catalyst was obtained by impregnation reduction method that Pd clusters were encapsulated into material channels.This catalyst could effectively catalyze the reduction of nitrobenzene in water under mild condition,because of the hydrophobic and lipophilic properties of the material.Compared with other Pd-based catalysts,Pd@3D-HPOPs catalyst is not only more efficient and stable,but also more green and environmental protection in the catalytic reaction process.This work not only provides a reference strategy for the fabrication of a stable and efficient Pd cluster catalyst,but also provides a milder and more green way for the degradation of aromatic nitro pollutants in water.(3)In this work,a single molecular cage HOF material containing hydrogen bonds was fabricated to further improve the loading capacity of metal clusters and obtain a more stable metal cluster catalyst.Ru@HOF catalyst was obtained by impregnation reduction method that Ru clusters were encapsulated in the cage.It was confirmed by characterization and catalytic experiments that the particle size of Ru was about 0.5 nm when the loading amount of Ru is 30 wt%,and the catalyst still maintained high activity and high stability in the reaction of reduction of Nheterocyclic compounds.This work solves the problem that the metal catalyst with high load is easy to agglomerate and provides a novel idea for selective reduction of Nheterocyclic compounds.The problem that metal cluster catalyst is unstable and easily agglomerates in the process of catalysis is solved effectively by anchoring metal culsters into porous organic materials in this study.The study provides a reasonable strategy for the construction of efficient and stable metal cluster catalyst.