Developing advanced porous materials possessing both a high storage capacity and selectivity for acetylene (C₂H₂) remains challenging but a sought-after endeavor. Herein we show a strategy involving synergic combination of spatial confinement and commensurate stacking for enhanced C₂H₂ storage and capture via maximizing the host–guest and guest–guest interactions. Two ultramicroporous metal-organic frameworks (MOFs), MIL-160 and MOF-303 are elaborately constructed to exhibit ultrahigh C₂H₂ uptakes of 235 and 195 cm³·g⁻¹, respectively, due to the confinement effect of the suitable pore sizes and periodically dispersed molecular recognition sites. Specially, C₂H₂ capacity of MIL-160 sets a new benchmark for C₂H₂ storage. The exceptional separation performances of two materials for C₂H₂ over both CO₂ and ethylene (C₂H₄), which is rarely observed, outperform most of the benchmark materials for C₂H₂ capture. We scrutinized the origins of ultrahigh C₂H₂ loading in the confined channels via theoretical investigations. The superior separation efficiency for C₂H₂/CO₂ and C₂H₂/C₂H₄ mixtures with unprecedented C₂H₂ trapping capacity (> 200 L·kg⁻¹) was further demonstrated by dynamic breakthrough experiments.