Preparation And Catalytic Properties Of Pyr-GDY

Graphdiyne(GDY),as a kind of two-dimensional(2D)material,was formed by the combination of sp and sp~2 hybridized carbon atoms according to a certain periodic rule.As a new artificial 2D carbon material,due to its unique molecular configuration,uniform pores and highly?-conjugated structure,many attentions have been paid in many fields,such as semiconductor devices,catalysis,gas separation,biomedicine and energy conversion.Generally,the properties of materials are strongly dependent on their structures and morphologies,thus,plenty of researchers committed to the construction of GDY with various nanostructures.So far,although a great deal of research has been done on the regulation of the nanostructure and morphology of GDY,most studies were focused on the templates assistant and the adjustment of reaction conditions.It is still a challenge task to synthesize GDY with ideal structure and unique morphology.Based on the above research background,in this context,we used the"bottom-up"approach to modulate the nanostructures of GDY by changing the basic construction unit,and prepare a new pyrenyl graphdiyne(Pyr-GDY)with special structure and morphology.As a result,Pyr-GDY can be used as a noble metal particle substrate for various liquid phase catalytic reactions.The main research contents are as follows:1.The "bottom-up"synthesis of a new Pyr-GDY carbon material was described,in which an ultrafine nanofibers structure was constructed by the a modified Glaser-Hay coupling reaction of 1,3,6,8-tetraethynylpyrene(TEP)monomer.Electron microscopy results show that the diameter of the nanofiber is around 3~10 nm.Due to the strong?-?stacking interactions between the pyrene rings,the stacking rate of small pieces of Pyr-GDY nanosheets along the nanofiber direction should be faster than the coupling reaction rate of TEP monomer along the 2D Pyr-GDY nanosheets,thus the small pieces of Pyr-GDY nanosheets prefer to grow along the nanofiber direction to generate unique nanofibers rather than nanosheets.This attribution was strongly confirmed by the parallel synthesis of a pyrene-free GDY analogue(Phe-GDY)with 1,3,4,6-tetraethynylbenzene(TEB)as the monomer,of which the morphology is bulky 2D nanosheet rather than 1D nanofiber.The results showed that the directional regulation of GDY from 2D nanosheets to 1D nanowires can be realized by the"bottom-up"approach.2.Benefiting from the low reduction potential of Pyr-GDY(+0.23 V vs SHE),abundant terminal alkynyl and three-dimensional network structure.It can serve as an ideal substrate for electroless deposition and stabilization of Pd sub-nanometric catalyst(Pd-SNC),forming a Pd/Pyr-GDY composite with an average particle size of only 0.83 nm.On the basis of experiments and theoretical calculations,it is further shown that the structure of ultrafine nanofibers and the existence of terminal alkynes in Pyr-GDY are beneficial to the in situ formation and stability of Pd-SNPs.In comparison,Phe-GDY with similar molecular structure obtained larger Pd nanoparticles by the same chemical deposition method.It is indicated that Pyr-GDY is an ideal carbon material for in-situ nucleation and growth-stable metal sub-nanoparticles.3.The Pd/Pyr-GDY composite was used as catalysts for the reduction of nitroarenes and Suzuki-Miyaura coupling reaction respectively,and which shows extremely high catalytic activity.On the one hand,its excellent catalytic performance can be ascribed to the sub-nanometric Pd particles with"clean surface",which conducive to direct contact between the reaction substrate and the catalyst.On the other hand,the electron-rich nature of acetenyl groups,as well as the unique three-dimensional network structure of Pyr-GDY,are favorable for rapid mass transfer.