| Summary: | Metal–organic frameworks (MOFs) are regarded as the next-generation, disruptive membrane materials, yet the straightforward fabrication of ultrathin MOF membranes on an unmodified porous support remains a critical challenge. In this work, we proposed a facile, one-step electrophoretic deposition (EPD) method for the growth of ultrathin zeolitic imidazole framework-8 (ZIF-8) membranes on a bare porous support. The crystallinity, morphology and coverage of ZIF-8 particles on support surface can be optimized via regulating EPD parameters, yet it is still difficult to ensure the integrity of a ZIF-8 membrane with the constant voltage mode. In contrast, the constant current mode is more beneficial to the growth of a defect-free ZIF-8 membrane due to the steady migration rate of colloid particles toward the electrode. With a current of 0.65 mA/cm<sup>2</sup> and deposition time of 60 min, a 300 nm thick ZIF-8 membrane was obtained, which exhibits a CO<sub>2</sub> permeance of 334 GPU and a CO<sub>2</sub>/CH<sub>4</sub> separation factor of 8.8, evidencing the defect-free structure.
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