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Small: a variety of ultra fine and highly active metal nanoparticles with narrow size distribution can be controlled by using triphenylphosphine based COF as carrier

wallpapers News 2020-12-14

metal materials are widely used in the field of catalysis their catalytic activity is closely related to their size. The percentage of surface atoms of 1-2nm MNPs is as high as 80-90%. A large number of unsaturated bonds of surface atoms can be used as catalytic active centers. However the catalytic performance of 1-2nm MNPs is significantly reduced due to its high surface energy. Therefore it is a great challenge to control the preparation of ultrafine MNPs with narrow size distribution for heterogeneous catalysis. Organic porous carriers have many advantages such as various synthetic routes strong modifiability light weight high specific surface area adjustable pore size The narrow size dispersion of MNPs the excellent catalytic activity cycle stability of the catalytic materials are given by the synergistic effect of the support materials MNPs. However the related experiments show that it is difficult to achieve the controllable preparation of MNPs without the introduction of metal anchor sites. If the metal anchor sites can be evenly introduced into the organic porous support it is expected to realize the controllable preparation of 1-2 nm MNPs give them high catalytic activity high stability.

In order to realize this idea Qiu Li research group of

Yunnan University Zhang Wei research group of the University of Colorado selected triphenylphosphine as the metal anchor point which was covalently bonded into the framework of covalent organic framework through imine condensation reaction to obtain a novel nonplanar two-dimensional COF (phos-cof-1) which realized the homogeneous adsorption of triphenylphosphine in organic porous carrier Four kinds of MNPs (PD Pt Au PdAu) with high activity high stability were successfully prepared.

as ligs play an irreplaceable role in the stable existence of metal catalysts (especially palladium catalysts) due to the existence of lone electron pairs of P element in triphenylphosphine. However the separation recycling of small molecule homogeneous catalysts (tetratriphenylphosphine palladium dichlorodiphenylphosphine palladium etc.) is the bottleneck of their application in pharmacy fine chemical industry Therefore the key to solve this problem is to develop triphenylphosphine based heterogeneous catalytic materials. If triphenylphosphine is keyed into COF as a skeleton unit the uniform distribution of triphenylphosphine in COF can be achieved at the atomic level. If P is used as the interaction site between porous carrier metal source the uniform nucleation growth of MNPs in the carrier can be achieved. In addition the valve domain effect of COF can effectively prevent the agglomeration of MNPs in preparation recycling application 。 Pdnps (1.62 ± 0.37 nm) ptnps (2.06 ± 0.54 nm) AuNPs (1.78 ± 0.32 nm) pdannps (1.03 ± 0.07 nm) were prepared by a very simple chemical reduction method using phos-cof-1 as organic porous carrier k2pdcl4 k2ptcl4 HAuCl4 as metal source MeOH as solvent NaBH4 as reducing agent. Through the synergistic effect of triphenylphosphorus MNPs in COF the four catalytic materials showed excellent catalytic activity stability easy recovery in Suzuki Miyaura coupling reaction reduction of p-nitrophenol reduction of 1-bromo-4-nitrobenzene one pot coupling reduction of p-iodo-nitrobenzene. The design concept of controllable synthesis of ultrafine MNPs based on ordered porous materials with uniformly distributed metal anchor points is believed to develop a new research idea for controllable preparation of MNPs.

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