Low-cost, all-organic, hydrogen-bonded thin-film composite membranes for CO2 capture: Experiments and molecular dynamic simulations

Despite the excellent separation performance of organic-inorganic hybrid membranes, such as mixed-matrix membranes, their commercial application remains challenging due to difficulties in uniformly dispersing inorganic fillers and achieving good interfacial contact over large areas. In this paper, we present high-performance, thin-film composite (TFC) membranes made from low-cost, all-organic materials using a commercially attractive and straightforward process for CO2 capture. The TFC membranes were prepared on a porous polysulfone support using 2,4,6-triaminopyrimidine (TAP) dispersed in comb-shaped polymerized poly(oxyethylene methacrylate) (PPOEM), synthesized through a free radical polymerization process. The organic filler TAP functioned as a hydrogen bond inducer, controlling the free volume and reducing gas diffusivity, thereby enhancing CO2 selectivity over larger gases such as N-2 and CH4. Incorporating 2 wt% TAP significantly improved separation performance by primarily reducing N-2 and CH4 permeances, achieving a CO2 permeance of 1140 GPU, with CO2/N-2 and CO2/CH4 selectivities of 43.3 and 15.0, respectively. The achieved performance significantly surpassed that of Pebax-based membranes and successfully met the target criteria for post-combustion CO2 capture. Variations in free volume, molecule aggregation, hydrogen bonding, and interaction energies between gases and membranes were thoroughly investigated via molecular dynamic (MD) simulations. This high-performance TFC membrane, created through simple and facile methods using entirely organic materials, achieves commercial standards for post-combustion CO2 capture.