Study On Interlayer Fixation Of Two-Dimensional Covalent Organic Framework (COF) Containing Alkynyl Group

Ordered two-dimensional covalent organic frameworks(COF)derived from the reversible bond formation of thermodynamically controlled organic bonds have an expanded porous structure,high porosity,and precise atomic arrangement.In practical operations such as gas separation,optoelectronics and heterogeneous catalysis,many functional organic bonds are used to prepare COF materials with higher flexibility.The two-dimensional COF has specific aligned one-dimensional channels that vary from hexagons to triangles,quadrilaterals,and rhombuses,as well as double-porous and porous structures,by using appropriately designed building blocks.By introducing different linkers of different lengths,it is possible to precisely adjust the pore diameter of the 2D COF with small differences,and easily customize the function of the hole wall.The macroporous two-dimensional COF exhibits good performance in dye adsorption and chiral organic catalysis,thanks to the ultra-large pore size that enables the encapsulation and diffusion of macromolecular guests.In general,two-dimensional COF have a high degree of crystallinity.In addition to the geometry of the monomers that play a key role in forming stable layers,molecular interactions such as ?-? forces are also essential.The ?-? force between adjacent layers can stabilize the entirestructure,providing a complete organization of highly crystalline 2D or3 D interpenetrating frames.As a two-dimensional COF of a graphite analog,the ?-? force between layers is insufficient to resist sliding.Once the connections in the skeleton are removed,the debris will fall off the skeleton,resulting in amorphous features.As mentioned above,large-pore two-dimensional COF formed by longer joints or junctions will result in lower ? density,where the ?-? force is usually insufficient to meet the requirements for forming a high crystalline structure.To date,there have been few reports of large-pore two-dimensional COF,mainly due to its low stability.Here we report a new macroporous two-dimensional COF(JU-COF-1)synthesized from 1,3,5-tris(4-formylphenylethynyl)benzene and 4,4'-diaminobiphenyl with a pore diameter of 5.0 nm.With simple click chemistry of azide and alkynyl groups in the framework,the material can further withstand layer locking.Successful pinning layers and layers can confer coercive bond-to-layer interactions with this macroporous COF material,thereby improving acid stability.Even if the imine bond is mostly broken,the structure of interlayer covalently bonded COF(JU-COF-2)can exist stably.This strategy will provide new ideas for improving the instability of two-dimensional COF due to layer slip and the introduction of functional groups between layers.