Gabbia molecolare in membrana a matrice mista per la separazione di gas

The levels of CO2 in the atmosphere are daily increasing and, for this reason, the climate equilibrium is drastically and rapidly changing. To reduce the concentration of CO2 in the air, the scientific community is trying to develop new capturing systems for the industrial discharge. As of today, despite the many protocols and employed materials, an improvement in terms of costs and efficiency of the current technologies must be performed. Since the second half of the XX century, a series of gas-capturing materials has been developed in order to obtain filtering systems able to discriminate CO2 molecules from other gases, such as N2, H2 and O2; particular attention was given to the CO2/N2 separation. During the last years, an important development of specific membranes for gas separation was achieved; more recently, through the insertion of porous molecules in polymeric matrix, hybrid materials called Mixed Matrix Membrane (MMMs) were obtained with improved physical properties as well as permeability and selectivity for the target gases. Examples of porous molecular systems used as fillers in MMMs are Metal Organic Frameworks (MOF) and Covalent Organic Frameworks (COF). These reticular systems can be easily synthesized through simple procedures and with high yields; however, the scarce solubility of these compounds in organic solvents strongly affect the uniformity of the membrane, causing the formation of defects at the filler/membrane interface and, in some cases, reducing the efficiency of the MMMs. On the other hand, Porous Organic Cages (POC) are generally more soluble in organic solvents, allowing a better dispersion of the filler in the polymeric matrix and thus favouring the formation of a hybrid membrane without cracking or defects. The main problems linked to POCs are that they generally require high dilution for the synthesis, moreover the final yields can be very low. An improvement was given by the Dynamic Covalent Chemistry (DCC) approach, that exploits reversible organic reactions (as e.g. imine condensation and the formation disulphide bridges) to achieve cage-like molecules in high yields. This thesis applied the DCC approach to obtain new organic cages to be applied as fillers in the preparation of MMMs. The first part of my internship was focused on the preparation of new molecular cages, called Trip-m-C and Trip-p-C. To achieve this goal, I synthesised and characterized the building blocks and I performed several trials to obtain the final cages by imine condensation. The Trip-m-C was achieved in good yields, while all attempts to obtain Trip-p-C were unfortunately unsuccessful, leading to oligomeric networks instead of a closed cage-like molecule. The Trip-m-C cage was characterised both in solution and in the solid state, then it was brought to Cosenza (CS) for further physico-chemical investigations and for the preparation of MMMs. At the CNR-ITM I have developed new MMMs, using three different polymers (PEEK-WC, Matrimid® 5218 and Matrimid® 9725) containing 20%w Trip-m-C. The obtained MMMs were then tested with various gases: He, H2, O2, N2, CO2, CH4, in order to determine the permeability and selectivity of the new MMMs.