Syntheses,Gas Adsorption And Separation Properties Of Bicarbazole-Based Flexible-Robust Hydrogen-Bonded Organic Framework Materials

Hydrogen-bonded organic frameworks（HOFs）represent an intriguing type of crystalline porous materials that self-assemble through the hydrogen-bonding with organic bridging blocks,are one of the most rapidly developed porous materials over the past decade.In recent years,owing to the mild synthetic conditions,easy regeneration,solution processability,and high surface areas the bright potential of HOFs as emerging multifunctional materials is highlighted in many research areas,especially for gas storage and separation.Nowadays,mainly there are two types of porous materials used for energy gas separation.One is flexible materials that the pores are typically gradually enlarged under slightly higher pressures or temperatures,therefore they also entrap the larger hydrocarbon,leading to co-adsorption.Another is robust materials that allow the complete separation of one component from others based on molecular size or shape cut-off,avoiding the co-adsorption.However,it has remained difficult to prepare rigid porous materials for high sieving separations of hydrocarbons.It is a very important to solve the challenge that using a novel material with flexible-robust to realization of cost and energy efficient hydrocarbon compound.There areπ-conjugated carbazole molecules that endow the materials with high stability.At the same time,utilizing the flexibility of hydrogen bonds and changing the structure by changing the conditions of external stimulation（i,e,temperature,pressure）to improve the separation efficiency.In this dissertation,we aimed to synthesis the building block of 3,3′,6,6′-tetrabromo-9,9′-bicarbazole to fabricate high stability HOFs materials.The research work of this dissertation provides theoretical basis and new research ideas for the application of HOFs materials in the storage and separation of petrochemical gases（C2/C3）and the methods of constructing and optimizing HOF materials.We have successfully realized a flexible robust hydrogen-bonded organic framework（HOF-FJU-1）with high sieving separation for ethylene from ethane by tuning the adsorption gate-pressures at different temperatures.This novel approach has successfully minimized the co-adsorption of ethane while retained a significant amount of ethylene uptakes,leading to considersbly enhanced ethylene/ethane separation performance at the elevated temperatures.This HOF material can readily produce high-purity C₂H₄（>99%pure）from C₂H₄/C₂H₆ mixture in a fixed-bed column at 333 K,a temperature close to the real gas mixture streams in practical processes,indicating the bright promise of this flexible-robust porous material for the industrial C₂H₄/C₂H₆separation.Furthermore,HOF-FJU-1 is not only thermally stable but also stable in common organic solvents and p H values ranging from 1 to 14,even in solutions of 12M HCl and 10 M Na OH.These results reveal the great application potentials of HOF-based materials for realizing important gas separations.We have demonstrated that a hydrogen-bonded organic framework（HOF-FJU-1a）with stereoscopic binding trap can complete lock acetylene（C₂H₂）molecule,leading to the unusual phenomena in physical adsorption process.This HOFs exhibits the record-high IAST selectivity of 6675 at 323 K for 50/50 C₂H₂/CO₂ mixture,far exceeding the previously benchmark materials reported.The dynamic breakthrough experiment also demonstrated that HOF-FJU-1a can efficient separate C₂H₂/CO₂（v/v,50:50）at 323 K,a temperature close to the real gas mixture streams in practical processes.The single-crystal X-ray diffraction shows the abnormal-but-excellent C₂H₂binding affinity is owing to multiple C–H···πand hydrogen-bonded interactions.These results reveal the great application potentials of HOF-based materials for realizing important gas separations.We investigated utilization of organic building blocks to engineer a HOF material exhibiting an optimized pore aperture and cavity to address challenging C₃H₆/C₃H₈separations.The developed material,namely HOF-FJU-1,owing to the thermoregulatory gating effect,was successfully applied in molecular sieving of C₃H₆from C₃H₈ or other relative mixtures under convenient operation conditions.Notably,compared to known C₃H₆ sieving materials,such as Y-abtc,Co-gallate,and KAUST-7,HOF-FJU-1 displayed the highest C₃H₆ adsorption capacity(46.2 cm³ g^-1),C₃H₆/C₃H₈ uptake ratios（53）,and C₃H₆/C₃H₈（50/50）selectivity（616）at 333 K and 1 bar.The efficient thermoregulatory sieving separation of C₃H₆ was comprehensively analyzed by a combination of single-crystal structural evaluation,single-component adsorption tests,and various breakthrough experiments.Benefiting from the dynamic gating effect and rapid kinetic ad/desorption rate under high temperature,HOF-FJU-1 could be used for the production of high purity C₃H₆ from C₃H₆/C₃H₈ mixtures with a remarkably high separation productivity.The outstanding structural stability,high separation ability,and cycling performance further highlight the potential of this HOF adsorbent for application in separation processes requiring challenging conditions.We have successfully developed a new adsorption site T-shape aromatic space for efficient removal of acetylene from acetylene mixtures in a highly stability bicarbazole-based metal-organic framework,FJU-83.What’s more,FJU-83 is not only thermally stable but also stable in common organic solvents and p H values ranging from 1 to 12.The approch of this work is likely applicable to other gas mixtures,which will save energy in practical separation processes.