Research On The Preparation And Application Of Organic Framework Materials Based On Seven- And Eight-membered Cucurbit Ring

Cucurbit[n]urils（Q[n]s）have now become an important part in the field of macrocyclic and supramolecular chemistry,and with the continuous research on them,they have shown excellent properties in the direction of supramolecular materials.On the one hand,the rigid pumpkin-shaped structure with a hydrophobic cavity and two carbonyl ports is well suited as an excellent organic building block for new melon ring-based porous supramolecular frameworks.On the other hand,the positive electrostatic potential of the outer wall allows the melon ring to interact not only with the carbonyl port of the adjacent melon ring with negative electrostatic potential,but also with various inorganic metal anions,i.e.,the two most common types of melon ring outer wall interactions-self-induced and anion-induced outer wall interactions,which makes it easy to construct novel and specific melon ring-based supramolecular framework structures.Therefore,the strategy of constructing Q[n]-based supramolecular framework structures by the induction of Q[n]host-guest interaction and outer wall interaction can not only establish an effective method for constructing framework structures in Q[n]chemistry,but more importantly,the Q[n]-based supramolecular framework structures obtained by this construction strategy have broad application prospects in adsorption,selective trapping of metal ions,and special structured catalysts.In this paper,a series of studies on cucurbit[8]uril（Q[8]）were carried out.Six kinds of supramolecular frameworks are constructed in 6M hydrochloric acid aqueous medium.Six kinds of supramolecular frameworks have many similarities and differences.We have done some research on these six supramolecular frameworks.Firstly,by optimizing the synthesis and separation technology of cucurbit[n]uril,pure cucurbit[n]uril was prepared in a short period of time to prepare for the follow-up study.Furthermore,in the medium of 6M hydrochloric acid aqueous solution,different single crystal materials were obtained by using different induction reagents.Finally,the host-guest interaction based on cucurbit[8]uril（Q[8]）and the adsorption,desorption and detection properties of the materials prepared by the above methods were preliminarily studied.The binding interactions of cucurbit[8]uril（Q[8]）with L-Valine,D-Leucine,and D-Methionine,both in aqueous solution and solid state,have been studied by 1H NMR spectroscopy and X-ray crystallography.¹H NMR data indicate that Q[8]can encapsulate these three kinds of amino acids in aqueous solution.X-ray crystallography reveals how the Q[8]binds with the amino acids to form inclusion complexes L-Val₂@Q[8],D-Leu₂@Q[8],and D-Met₂@Q[8]through host-guest interactions.It was also found that the deformation degree of the Q[8]host is related to the molecular size of the encapsulated guests.A series of melon cyclic framework compounds QSF-1,QSF-2 and QSF-3 were prepared.X-ray crystallography showed that QSF-1 was a tubular channel induced by metal iron.By using the porosity and adsorption properties of the supramolecular framework,the material was used to adsorb various volatile gases.The results showed that fluorescence quenching occurred when QSF-1 adsorbed pyridine gas.X-ray crystallography showed that both QSF-2 and QSF-3 structures contained many channels.The results showed that both QSF-2 and QSF-3 had adsorption properties.These two materials are used to adsorb various volatile gases.The results showed that:（1）when QSF-2 adsorbed ethanol gas and tetrahydrofuran gas,the fluorescence intensity decreased greatly,and with the longer adsorption time,the fluorescence intensity decreased continuously,and the fluorescence intensity did not change after reaching the adsorption saturation;（2）When QSF-3 adsorbed pyridine gas and toluene gas,the fluorescence intensity decreased greatly,and with the longer adsorption time,the fluorescence intensity decreased continuously until the adsorption saturation.