A Charge-Density-Tunable Three/Two-Dimensional Polymer/Graphene Oxide Heterogeneous Nanoporous Membrane for Ion Transport

The design and fabrication of a robust nanoporous membrane in large scale is still a challenge and is of fundamental importance for practical applications. Here, a robust three/two-dimensional polymer/graphene oxide heterogeneous nanoporous membrane is constructed in large scale via the self-assembly approach by chemically designing a robust charge-density-tunable nanoporous ionomer with uniform pore size. To obtain a nanoporous polymer that maintains high mechanical strength and promotes multifunctionality, we designed a series of amphiphilic copolymers by introducing a positively charged pyridine moiety into the engineered polymer polyphenylsulfone. The multiphysical-chemical properties of the membrane enable it to work as a nanogate switch with synergy between wettability and surface charge change in response to pH. Then we systematically studied the transmembrane ionic transport properties of this two-/three-dimensional porous system. By adjusting the charge density of the copolymer via chemical copolymerization through a controlled design route, the rectifying ratio of this asymmetric membrane could be amplified 4 times. Furthermore, we equipped a concentration-gradient-driven energy harvesting device with this charge-density-tunable nanoporous membrane, and a maximum power of ≈0.76 W m-2 was obtained. We expect this methodology for construction of a charge-density-tunable heterogeneous membrane by chemical design will shed light on the material design, and this membrane may further be used in energy devices, biosensors, and smart gating nanofluidic devices.