Two-dimensional framework membranes (2DFMs) hold great promise for sustainable energy-harvesting technologies, yet their performance is often limited by low electric double-layer (EDL) coverage (ƞ_EDL) arising from large channels and/or low charge densities. Here, we report an ultrathin (~ 50 nm), fully crystalline, ABC-stacked viologen-incorporated 2D polymer membrane (sV2DP) featuring vertically aligned triangular nanochannels (D_eff = 1.36 nm) densely decorated with pyridinium sites (+ 22.4 mC m⁻²). Compared with its non-staggered AA-stacked analogue, sV2DP exhibits a 3.2-fold enhancement in ƞ_EDL under a 50-fold KCl gradient, combining high anionic selectivity (t₋= 0.85) with remarkable selective current density (14.6 kA m⁻²). Simulations reveal that spirally arranged charges generate a unique “screw-like” anion migration pathway, significantly enhancing transmembrane efficiency relative to non-staggered 2DP analogues. When integrated into micro-aperture osmotic power generators, the sV2DP membrane delivered a peak power density of 243 W m⁻² under a 50-fold NaCl gradient, placing it among the highest-performing systems.