Bioinspired Fabrication of Polydopamine–Based Membranes for Gas Separation

Abstract: Facile fabrication of composite membranes with ultrathin, defect-free and stable active layer is one of the key issues in scaling up numerous energy-related dense membrane processes such as gas separation, gasoline desulfurization and alcohol dehydration, etc. Inspired by marine mussel’s bioadhesion phenomenon and principle, a facile and versatile approach for fabricating composite membranes with ultrathin and stable active layer by coating dopamine on microporous substrates followed by polymerization and post treatment was presented. The thickness and the free volume of the polydopamine layer could be tailored by varying dipping conditions including the dopamine concentration, dipping time and pH value of the solution. Then, polymer–inorganic hybrid membranes were prepared by using polymeric materials as the membrane bulk matrix and metal ions-reinforced polydopamine nanoaggregates as the filler. The structure of the hybrid membrane could be tuned by varying the composition of the organometallic nanoaggregates, resulting in the well-controlled size-dependent transport of gas molecules. Alternatively, an additional layer of polyethyleneimine was coated on the polydopamine membrane. The resultant polyethyleneimine-coated polydopamine membrane exhibited simultaneously high CO₂ permeance, high CO₂/CH₄ selectivity and high stability. We hope these findings open an effective approach to large-scale fabrication of high-performance composite membranes for gas and other energy-related separations.