The preparation of carbon materials based hydrogels and their viscoelastic properties are essential for their broad application and scale-up. However, existing studies are mainly focused on graphene derivatives and carbon nanotubes, and the behavior of graphene nanoribbon (GNR), a narrow strip of graphene, remains elusive. Herein, we demonstrate the concentration-driven gelation of oxidized GNR (graphene oxide nanoribbon, GONR) in aqueous solvents. Exfoliated individual GONRs sequentially assemble into strings (∼1 mg/mL), nanoplates (∼20 mg/mL), and a macroporous scaffold (50 mg/mL) with increasing concentration. The GONR hydrogels exhibit viscoelastic shear-thinning behavior and can be shear-coated to form large-area GONR films on substrates. The entangled and stacked structure of the GONR film contributed to outstanding nanofiltration performance under high pressure, cross-flow, and long-term filtration, while the precise molecular separation with 100% rejection rate was maintained for sub-nanometer molecules.

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Although the pore structures and gas transport properties of metal‐organic frameworks (MOFs) have been tuned mainly by modifying the framework building blocks, a pore‐tuned zeolitic imidazolate framework (ZIF)‐8 layer is directly grown on graphene oxide nanoribbons (GONR)‐treated polymer substrate. Oxygen‐containing functional groups and GONR dangling‐carbon bonds facilitated the spontaneous growth of ZIF‐8 oriented to the (100) grain on the GONR surface and also enhanced the rigidity by strongly anchoring the ZIF‐8 layer by metal‐carbon chemisorption. Gas permeation and molecular simulation results confirmed that the effective aperture size of ZIF‐8 is adjusted to 3.6 Å. As a result, ultrafast H2 permeance of 7.6 × 10−7 mol m−2 Pa s is achieved while blocking large hydrocarbon molecules. In particular, the membrane showed exceptionally enhanced hydrogen selectivity for the mixture separation than ideal selectivity, owing to the competitive transport between H2 and large hydrocarbon molecules, and the separation performance surpassed those of ZIF membranes previously fabricated on polymeric supports.

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