Enhanced CO₂ capture through bulky poly(urethane-urea)-based MMMs containing hyperbranched triazine based silica nanoparticles

Two types of poly(urethane-urea)-based mixed matrix membranes containing hyperbranched structures of surface-modified silica nanoparticles were fabricated. The stepwise surface modification of nanoparticles was done based on aminopropyltriethoxysilane, cyanuric chloride, and ethylenediamine. FTIR, TGA, elemental analysis, and SEM-EDX were served to characterize the modified particles. The incorporation of the nanoparticles into poly(urethane-urea)s (PUUs) altered the phase separation degree of soft and hard segments, elevated the glass transition of soft segments and reduced the chain order. MMM containing the optimal distribution of 5 wt% modified silica showed improved mechanical and gas separation properties with 20–25% and 30–36% enhancement in CO₂ permeability and CO₂/N₂ selectivity, respectively. The presence of long adsorbent chains with NH moieties on the particles improves the particle distribution in the matrix, thereby enhanced CO₂ permeability up to 5 wt% particle content. At higher loadings, the agglomeration of the particles led to the formation of non-selective channels for gas diffusion and reduced gas separation performance and mechanical properties.