CO2 Capture by Metal-Organic Framework based Mixed Matrix Membranes (MMMs)

Membrane separation is an energy efficient technology with a small physical footprint in which the membrane is the core of process. Membranes need to be further developed to be specifically applied in the field of gas separation. The most challenging target in designing membranes is to improve the permeation and selectivity, simultaneously. This goal cannot be achieved without acquiring the knowledge of material science to tune the membrane material properties. This PhD thesis focusses on designing mixed matrix membranes (MMMs) by using a new class of crystalline materials known as metal organic frameworks (MOFs) as filler. In combination with polymers as continuous phase it was expected to improve both the processability and separation performance of this composite material in comparison with the polymer only. This work has been performed in the framework of the FP7-EU project M4CO2 ('MOF-based Mixed Matrix Membranes for energy efficient CO2 capture', grant agreement n° 608490). Therefore the focus in this thesis was on, but not limited to, membranes for the separation of CO2 from N2, as a model for stack gases in coal combustion ('post-combustion separation'). To this aim, the overall concept of this thesis is divided into three parts in which the most relevant aspects of design in mixed matrix membranes are carefully studied. Part I (Chapter 2) elucidated the influence of MOF pore structure and topology on the MMMs separation performance. In part II (Chapter 3 and 4) the effect of MOF morphology and polymer free volume is studied. Finally, part III (Chapter 5) reports a study on free-standing and thin supported MOF nanosheet based membranes by using industrially viable methods. The summary of each Chapter in this thesis is presented as follows...