Design And Synthesis Of Metal-organic Frameworks For Seperation Ang Recovery Of Hydrocarbons

Metal-organic frameworks(MOFs),emerging as a new class of crystalline nanoporous materials assembled by secondary building units and organic linker,have becom one of hottest topics of research in wide range of fields of science,such as separation,chemical sensing,catalysis,and energy conversion,due to their unique characteristics including extra-high surface area and adjustable pore size as well as facile functionalization.Separation and purification processes are critically important for modern chemical industry as to isolate pure or purer components from chemical mixtures and protect environment.This work mainly focuses on using MOFs as separating agents for the separation and recovery of hydrocarbons.The main works are as follows:1.Molecular sieving is a highly efficient method for gas separation because of ultra-high selectivity.Nevertheless,traditional adsorbents with molecular sieving effect can only separate a specific gas mixture due to their constant pore apertures.It is still a challenge to continuously fine-tune pore apertures at sub angstrom scale to separate various gas mixtures in a given porous material.Herein,temperature-responsive smart molecule gate with precisely controllable pore size is proposed and validated for molecule recognition and separation,achieved by introducing methoxyl group in the narrow bottleneck of the metal-organic framework(MOF).The effective aperture size of the smart molecule gate can be continuously tuned from 3.6 to 5.2 A,covering the size range of the commercially important gas molecules.Consequently,the MOF with such structure exhibits highly selective uptake for several gas mixtures,including N2/CH4,CH4/C2H4,C2H4/C3H6,C3H6/C3H8,and C3H8/i-C4H10,by controlling the opening degree of smart molecule gate.Furthermore,to verify the practical application,C3H6/C3H8 separation performances were systematical evaluated,and excellent selectivity for C3H6/C3H8 can be achieved at room temperature.This rational design of smart molecule gate in this work opens a new avenue for the application of smart materials for gas separation.2.Recovery of propylene from polypropylene(PP)purge stream is of great importance due to both more efficient conversion of the monomers and mitigation of pollutant emissions.Herein,a series of metal-organic frameworks(MOFs)were synthesized and their performances on C3H6/N2 separation were studied.The results indicate that CAU-1,an Al-MOF with ultra-microporous structure and amine-decorated function site,shows prominent C3H6/N2 liming selectivity among these MOFs.The IAST selectivity of CAU-1 is up to 236 under ambient condition,surpassing other reported porous materials.In addition,the high recovery efficiency(?99%)obtained by breakthrough experiments,good regenerability and high stability under harsh chemical conditions suggest the great potential of CAU-1 in practical industrial application.Our work demonstrates that the ultra-microporous structures and polar groups in CAU-1 play key roles for C3H6/N2 separation,which provides a guideline to design and synthesize high-performance MOFs in propylene recovery from polypropylene off-gas.3.Recovery of hydrocarbons from petrochemical process streams is of great importance due to both more efficient conversion of the monomers and environmental protection.A series of isostructural MOF-74-M materials(M=Mg,Co,and Cu)with proer pore sizes and highly dense unstaturated metal sites have been studied for the selective adsorption of hydrocarbons over petrochemical process streams.As a result,MOF-74-Co shows prominent C3H6/N2 and C2H4/N2 separating selectivity among these MOFs.The IAST selectivity of MOF-74-Co is up to 7568 and 432 under ambient condition,respectivity.Meanwhile,the olefin adsorption capacity on MOF-74-M remain unchanged even after five cycles.This work paves a new way to to design and synthesize high-performance MOFs in hydrocarbons from petrochemical process streams.