Construction Of MOF-LDHs Multilevel Structural Material And Its Application On Series Catalytic Performance

In the face of the rapid development of society and the increasing progress of science,how to effectively reduce the cost and reduce the excessive consumption of energy is of practical importance for the achievement of the sustainable development.In the field of chemistry,the integration of multi-step synthesis into a one-pot series catalytic process can not only simplify operation,reduce energy consumption and product loss,but also coupling multiple chemical reactions in a system can achieve more effective heat and mass transfer control,which can effectively reduce costs,and is of great significance for sustainable chemistry.Metal-organic skeleton materials(MOFs)are widely used in energy storage,photocatalysis and gas separation due to their advantages such as high porosity,large specific surface area and pore regularity.Layered double hydroxides(LDHs)have broad application prospects in heterogeneous catalysis due to their chemical composition,adjustable anions between layers,large specific surface area and abundant basic sites.This paper mainly focuses on the study of the composite of MOFs and LDHs and its catalytic performance.The specific research contents are as follows:1.The regular octahedral structure of MOF is retained by encapsulating the polyacid,and CuCo-LDH is used to catalyze the acid-base series reaction: Using NENU-9 as precursor,NENU-9@CuCo-LDH composite with multistage structure was prepared by in-situ growth method.It was used in acid-base series reaction,and the best reaction condition was obtained by adjusting the solvent,reaction temperature and other conditions as well as kinetic experiments.Experimental results show that NENU-9@CuCo-LDH,which achieves spatial separation of acid-base sites at 90℃ and 7h without solvent,has good catalytic performance for acid-base series reaction.The conversion rate of benzaldehyde dimethylacetal as the reactant is greater than 99%,and the yield of α-cyano-ethyl cinnamate as the final product is greater than 99%.This work provides a research basis for constructing multilevel structural materials and realizing spatial separation of active sites.2.Regulation of selective growth of outer CuCo-LDH crystal surfaces with different morphologies of NENU-3 and study on the series reaction performance: Three kinds of NENU-3 with different morphologies were synthesized.The crystal surface selectivity of CuCo-LDH growth was investigated by adjusting the hydrothermal temperature,time,metal salt concentration,the amount of alkali urea and other conditions,so as to obtain the NENU-3@CuCo-LDH nanocomposite with the same multistage structure.The selectivity of benzyl alcohol substrates exposed with different crystal faces to large substrates was verified by selecting a series of benzyl alcohol substrates with different sizes.This method provides a feasible scheme to overcome the limitation of the microporous skeleton of MOF on the diffusion of high steric hindrance substrate.