Mixed matrix membranes containing well-designed composite microcapsules for CO2 separation

Hollow fillers with tailored nanostructures and functionalities have become promising candidates for advanced mixed matrix membranes (MMMs). Herein, polydopamine/poly (ethylene glycol) (PEG) composite microcapsules are synthesized by hard template method and embedded into the Pebax matrix to fabricate MMMs for CO2 capture. As a well-known biomimetic adhesive, polydopamine in the capsule wall renders adequate polymer-filler interfacial adhesion. The template removal process produces through-wall mesopores, which allow rapid gas diffusion into the lumen, further significantly reducing the trans-membrane mass transfer resistance. The remaining PEG in the capsule wall not only increases CO2 affinity, but also avoids excessive chain rigidification at polymer-filler interface. In this way, the composite capsules, compared with those without PEG, confer significantly enhanced separation performance on membranes. The optimal gas transport property of the resultant membranes is obtained with a CO2 permeability of 510 Barrer and an ideal selectivity of 84.6 for CO2/N2 at humidified state, i.e., 108%, 98% higher than those of neat Pebax membrane, respectively. In addition, owing to dopamine-enabled strong adhesion, the MMMs exhibit better stability than Pebax membrane in the long-term test at 85°C.