<p>Biological ion channels exemplify nature’s high-efficiency ion selectivity filters, yet replicating their functional architectures in synthetic membranes remains a fundamental challenge. Here, we report an ultramicroporous hydrogen-bonded organic framework membrane that structurally emulates the CLC chloride filter. Its channels exhibit size adaptability to anions and incorporate hydrogen-bond donors that provide “low-viscosity” compensatory interactions, thereby alleviating anion dehydration energy penalties. By leveraging differential dehydration and energy compensation between Cl⁻ and larger anions such as SO₄²⁻, this bioinspired design achieves an exceptional Cl⁻/SO₄²⁻ selectivity of over 400—several tens of times higher than those of existing counterparts—while maintaining a high Cl⁻ permeation rate double that of the commercial Neosepta^® ACS membrane, setting a new benchmark for advanced anion-sieving membranes. In electrodialysis (ED) for high-salinity wastewater valorization, our membrane enables higher NaCl product purity (99.62 wt% vs. 72.86 wt%) with 28.7% lower energy consumption than the Neosepta^® ACS membrane. This work establishes a biomimetic design principle of biological anion channels that is potentially extendable to a wide range of selective and conductive membranes.</p>