Synthesis And Application Of 3D COF With Novel Topology Based On Triptycene

Covalent organic frameworks（COFs）are a new type of crystalline organic porous materials that combine network chemistry and dynamic covalent chemistry,and are formed by reversible covalent reactions between organic modules.Their attractive features,such as high surface area,high porosity,and tunable pore environment,make COFs great candidates for gas storage/separation,organic electronics,heterogeneous catalysis,and a number of other fields.COFs have periodic network structure and a specific organic building unit,resulting in its structure and properties directly related to the symmetry and connectivity of the monomer used.In the more than ten years of the rapid development of COFs,most reports focus on 2D COFs withπ-πstacking structure generated by the polymerization of coplanar 2D polygonal monomers.In contrast,on the one hand,the available three-dimensional organic monomers are scarce due to the limited geometry and the small number of extended nodes formed by the hybridization of sp,sp² and sp³of carbon,on the other hand,the relatively complex structure and more difficult synthesis conditions lead to less research on 3D COFs.At present,almost all reported3D COFs are constructed by using tetrahedral（4-linked）building blocks,including derivatives of tetraphenylmethane,tetraphenylsilane and adamantane,which greatly limits the structural diversity and functionalization of 3D COFs.However,3D COFs are regarded as a potential platform for molecular storage and separation due to its unique characteristics,such as penetrating porous structure,ultra-low skeleton density and easily accessible active sites.Therefore,it is of great significance to develop 3D COFs with different topologies and functions.Due to its unique rigid 3D scaffold structure,triptycene and its derivatives have been widely explored in a variety of porous polymer material platforms,such as porous aromatic frameworks（PAFs）,conjugated microporous polymers（CMPs）,intrinsic microporous polymers（PIMs）and covalent triazine frames（CTFs）.Although the rigid blade shape of triptycene is believed to prevent the accumulation ofπ-πand give the material a high surface area,the porous materials based on triptycene and its derivatives currently reported are usually amorphous and lack clear pore structure.Therefore,it is of great significance to design appropriate building units of triptycene and combine them with crystalline porous materials to clarify the unique pore structure brought by triptycene and improve the properties of porous materials.Based on the consideration of the above problems,we designed and synthesized three kinds of 3D COFs with different topologies based on triptycene,and studied their applications in gas storage and separation.The specific research content is divided into the following three parts:（1）Due to the scarcity of high-connectivity building units,the development of three-dimensional covalent organic frameworks（3D COFs）with new topologies remains a major challenge.In the first chapter,we designed and synthesized two new3D COFs with ceq topology（JUC-568 and JUC-568-F）by combining the triangular prism（6-connection）node and the plane triangle（3-connection）.Our approach to creating 3D COFs with novel topologies is based on the well-known symmetry-guided design principle.Triptycene derivatives,2,3,6,7,14,15-hexa（4′-formylphenyl）triptycene（HFPTP）and 2,3,6,7,14,15-hexa（4’-formylphenyl）triptycene（HFPTP-H）,can function perfectly as a highly symmetrical triangular prism node.We discovered that there are numerous feasible topologies for the combination of 6-connected and 3-connected build units,such as ceq,sab,and dag,after analyzing the Reticular Chemistry Structure Resource（RCSR）database.As a result of the condensation of HFPTP/HFPTP-H and a planar triangle（3-connected）monomer,2,4,6-tris（4-aminophenyl）-1,3,5-triazine（TAPTA）,an expanded[6+3]connected network is formed（JUC-568）.Finally,Materials Studio（MS）simulation and powder X-ray diffraction（PXRD）were used to determine the structures of JUC-568 and JUC-568-F.The targeted material is more likely to form the ceq topology based on their link angles（60^o for HFPTP and 120^o for TAPTA）.Furthermore,both materials exhibit permanent porosity and impressive performance in CO₂ adsorption（98 cm³/g at 273 K and 1 bar）,CH₄ adsorption（48 cm³/g at 273 K and 1 bar）,and especially H₂ adsorption（up to 274cm³/g or 2.45 wt%at 77 K and 1 bar）,which is the highest among porous organic materials reported to date.Thus,this study offers a promising strategy for diversifying3D COFs based on complex building blocks,as well as promoting their potential applications in energy storage and environmental fields.（2）In chapter 2,based on the stereohexa-linked triptycene,we further introduced highly aromatic hexa-nodes into 3D COFs,and synthesized the JUC-641 and JUC-642with nia topology for the first time.It is worth noting that both COFs have high crystallinity,through-hole structure,excellent stability and large specific surface areas.We believe that triphenylene derivatives can provide abundant aromatic systems,while tripterylene,which has a rigid ring structure resembling a three-bladed,can both produce inherent micropores by generating internal free volume and breaking the conjugated structure within the skeleton to produce isolated aromatic systems.These can increase the interaction between COFs and Bz.More importantly,owing to a suitable pore channel and high aromatic skeleton structure,the synthesized COFs exhibit excellent separation ability for benzene and cyclohexane,and the ideal selectivity of benzene/cyclohexane is as high as 2.02,which is the greatest among the current 3D COF materials.Additionally,the consistency between the separation ratio of JUC-642 to benzene and cyclohexane（1.91）and the ideal separation ratio was proved by the breakthrough experiment.The interaction between COF frameworks and benzene was explored by DFT calculation of model molecules.The calculation shows that the interaction between benzene and adsorption site is better than that of cyclohexane,and the introduction of F atom can significantly enhance the interaction between the framework and guest molecules.In addition to laying the groundwork for the green separation application of organic porous adsorbents in the petrochemical industry,this study broadens the synthetic route of 3D COFs.（3）In Chapter 3,based on triptycene,we designed and synthesized a new six-linked amino building block,2,3,6,7,14,15-hexa（3′,5′-diisopropyl-4′-amino）triptycene（HDIATP）,which expanded the high-linked building blocks available for 3D COFs synthesis.Based on the principle of symmetry-guided design,we use the triptycene derivative 2,3,6,7,14,15-hexa（4′-formylphenyl）triptycene（HFPTP）as a highly symmetric triangular prism node.After analyzing the Reticular Chemistry Structure Resource（RCSR）database,we found that only one possible topology（acs）is available for such a 6-connected node.Furthermore,to construct a pure 6-connected framework,another triangular prism monomer,2,3,6,7,14,15-hexa（3′,5′-diisopropyl-4′-amino）triptycene（HDIATP）was also designed.JUC-569 can be obtained from the combination of two triangular prism monomers,HFPTP and HDIATP,with the same 6-connected node and link angle of 120°,which tends to a non-interpenetrated acs topology.Based on its unique rigid ring skeleton of triptycene,we further carried out various gas adsorption experiments on it.The research results show that JUC-569 has a high BET specific surface area（1254 m²/g）and a unique rigid ring skeleton of tripterylene,and shows excellent performance in adsorbing CO₂（47 cm³/g at 273 K and 1 bar）,CH₄（19 cm³/g at 273 K and 1 bar）,and H₂（167 cm³/g or 1.49 wt%at 77 K and 1 bar）.This work provides a new three-dimensional building block for the synthesis of 3D COFs and enriches the application of 3D COFs in the storage of greenhouse and energy gases.