Blue energy converts the chemical potential difference from salinity gradients into electricity via reverse electrodialysis and provides a renewable source of clean energy. To achieve high energy conversion efficiency and power density, nanoporous membrane materials with both high ionic conductivity and ion selectivity are required. Here, we report ion transport through a network of holeygraphene-like sheets made by bottom-up polymerization. The resulting ultrathin membranes provide controlled pores of <10 Å in diameter with an estimated density of about 10 12 cm −2 . The pores' interior contains NH 2 groups that become electrically charged with varying pH and allow tunable ion selectivity. Using the holey-graphene-like membranes, we demonstrate power outputs reaching hundreds of watts per square meter. The work shows a viable route toward creating membranes with high-density angstrom-scale pores, which can be used for energy generation, ion separation, and related technologies.
Biological ion channels use both their sizes and residual groups to reject large ions and molecules and allow highly selective permeation of small species with similar sizes. To realize these properties in artificial membranes, the main challenge is the precise control of both the channel size and the interior at the nanoscale. Here we report the permeation of ions and molecules through interlayer channels in graphene-based laminar membranes. The amino groups decorated on channel walls are found to form hydrogen bond networks with intercalated water molecules, thus providing a highly stable laminate structure and a controlled channel size. Solutes with hydration diameters of >10 Å are precisely sieved out. Small species permeate through with selectivities of up to a few thousand, governed by their distinct electrical interactions with channels depending on the atomistic distance from the charged species to the channel walls. Our work offers important insights into manipulating channel structures for enhanced separation performance at the nanoscale.
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