Porous Frameworks-based Membranes For Selective Separation Of Gases

In keeping with the thriving world economy and population growth trends,carbon dioxide emissions are on the rise posing environmental threats.To add to this issue,the demand for energy continues its upsurge.The adoption of membranes for carbon dioxide capture is exceedingly promising in terms of energy sustainability,selectivity,together with other merits.Albeit inimitably promising,polymer membranes have certain shortcomings such as low stabilities,low gas separation selectivities etc.The introduction of crystalline porous frameworks such as metal-organic frameworks(MOFs)etc.has helped to realize high-performing membranes by virtue of tunable features and tailor-made functionalities of MOFs.Despite the abundance of MOF membranes,covalent-organic frameworks(COFs)have not yet been adequately explored for gas-separation membranes.MOFs as well as COFs present immense potential in the fabrication of high quality gas separation membranes imparting with superb performance in terms of selectivity as well as permeability.This doctoral thesis is devoted to explore the potential of porous frameworks-based membranes for gas separation applications as well as study the compatibility between different porous frameworks that constitute composite membranes.Notably,the composite membranes referred to in this thesis comprise multiple pure-phase continuous matrices(chemically and structurally explicit layers)of different porous frameworks wherein the selective layer of the composite membranes encompass the constituent explicit layers of different porous frameworks as well as the interlayer between them.The thesis mainly comprises three parts as follows:Chapter 2 describes the coordination modulation approach guided fabrication,characterization and performance analysis of a UiO-66,a Zr-based MOF,gas-separation membrane.The membrane gives commendable gas separation performance.In Chapter 3,we report for the first time an oriented two-dimensional COF membrane consisting of ordered one-dimensional channels directly visible under high-resolution transmission electron microscopy,grown on the UiO-66 membrane that presents an incredibly high H2 permeability of 108341 Barrer and H2/CO2 mixture gas separation selectivity of 32.The COF-MOF compatibility was explicable by the imaging of the interlayer as well as interaction between zirconium cations and the amine groups of porphyrin supported by the Fourier transform infrared spectra.The approach used to obtain the[2D COF]-[MOF]composite membrane is unique and intriguing.The gas separation performance and gas permeabilities of the membrane are ultrahigh.In Chapter 4,we report a COF-300 membrane grown atop a UiO-66 membrane to fabricate a[COF-300]O[Ui0-66]composite membrane that demonstrates a synergic enhancement in H2/CO2 gas mixture separation performance as compared to the respective UiO-66 and COF-300 membranes.The porous frameworks selected to fabricate composite membranes were selected logically and understandably.To conclude,this research study aimed to analyze the gas separation performance of porous frameworks-based membranes as well as explore the surface interactions and interlayer imaging in composite membranes to interpret the enhancements in gas separation performance by the composite membranes.The study covers the fabrication approaches,binding interactions,characterization and separation applications of microporous frameworks based membranes.