Nano-materials Derived From MOFs And Their Catalytic Properties In The Selective Hydrogenation Of Phenols

Metal organic frameworks(MOFs)are a new class of porous materials which have shown great potential for application in heterogeneous catalysis.More recently,the use of MOFs as sacrificial template for preparation of MOFs derived metal-carbon based catalysts by pyrolysis at high temperatures has received considerable attention considering their relatively low thermal stability.On the other hand,the selective hydrogenation of phenol is an attractive routine to produce cyclohexanol that is an important basic chemical in chemical industry,but the design and synthesis of cost-efficient and highly selective catalysts remain a great challenge.In this thesis,considering the poor thermal stability and diversity of metal centers of MOFs,we selected MOFs with multi-metal centers as sacrificial templates for the preparation of MOFs derived materials,which were used as highly efficient heterogeneous catalysts for selective phenol hydrogenation,with cyclohexanol as the sole product.These catalysts consisting of bimetallic Ni-Co alloy nanoparticles(NPs)encapsulated in N-doped carbon matrix were simply synthesized by using our previously developed MOF-templated strategy.The sum of characterization results revealed that the Co and Ni elements were successfully alloyed in every individual NPs that were confined by N-doped carbon layers.Detailed catalytic test results suggested that both the pyrolysis temperature and the composition of these alloy NPs played the key roles in guiding their catalytic performance in the selective hydrogenation of phenol.It has been shown that Co-Ni@NC system was much more effective for hydrogenation of phenol than the Cu@NC,Co-Cu@NC and Ni-Cu@NC systems.The optimal 1Co-1Ni@NC catalyst could completely catalyze the hydrogenation of phenol to >99.9% cyclohexanol under conditions of 100 °C,0.8 MPa H2,which was approximately 2.8-and 4.3-fold higher than that of the Co@NC and Ni@NC respectively,revealing a strong positive synergistic effect between Ni and Co for this reaction.The kinetics study revealed that cyclohexanol was formed directly by the one-step hydrogenation of phenol in our catalyst system.This one-step pathway could avoid the formation of other hydrogenated intermediate product thereby leading to >99.9% selectivity of cyclohexanol.Furthermore,this catalyst also showed good recyclability,magnetically reusability and general applicability for a wide range of phenol substrates,which together with the superior activity and selectivity make it a good potential for the industrial applications.