Covalently Functionalized Nanopores for Highly Selective Separation of Monovalent Ions

Biological ion channels possess prominent ion transport performances attributed to their critical chemical groups across the continuous nanoscale filters. However, it is still a challenge to imitate these sophisticated performances in artificial nanoscale systems. Herein, this work develops the strategy to fabricate functionalized graphene nanopores in pioneer based on the synergistic regulation of the pore size and chemical properties of atomically thin confined structure through decoupling etching combined with in situ covalent modification. The modified graphene nanopores possess asymmetric ion transport behaviors and efficient monovalent metal ions sieving (K+/Li+ selectivity approximate to 48.6). Meanwhile, it also allows preferential transport for cations, the resulting membranes exhibit a K+/Cl- selectivity of 76 and a H+/Cl- selectivity of 59.3. The synergistic effects of steric hindrance and electrostatic interactions imposing a higher energy barrier for Cl- or Li+ across nanopores lead to ultra-selective H+ or K+ transport. Further, the functionalized graphene nanopores generate a power density of 25.3 W m-2 and a conversion efficiency of 33.9%, showing potential application prospects in energy conversion. The theoretical studies quantitatively match well with the experimental results. The feasible preparation of functionalized graphene nanopores paves the way toward direct investigation on ion transport mechanism and advanced design in devices. The functionalized graphene nanopores exhibit distinct monovalent ions transport behaviors including transport-rectification and exquisite intercation or anion/cation selectivity through precise pore structure and surface functional groups regulation. These prominent performances not only strongly rely on the ultra-low permeability resistance of atomically thin graphene but also attribute to the synergistic effects of steric hindrance and electrostatic interactions.image