We constructed a robust microporous metal-organic framework (MUM-15) possessing two types of functionalized tri-mural nanotraps, in which elaborate nano-space and specific pore environment are beneficial to form pore confinement effect and multiple strong interactions for C2H2. NUM-15 demonstrates not only remarkable sorption capacity for C2H2 but also exhibits excellent separation performance for intractable C2H2/CO2 and C2H2/C2H4 mixtures. Display omitted •The strategy for constructing nanotraps was proposed and a novel MOF was successfully designed and synthesized.•The tailor-made tri-mural nanotraps provided pore confinement and synergetic multiple interaction sites for C2H2.•Both high uptake capacity and strong affinity for C2H2 were realized.•The MOF exhibits excellent separation ability for C2H2/CO2 and C2H2/C2H4 mixtures under ambient conditions. Considering the tremendous significance of purification and capture for acetylene (C2H2) in the fields of manufacturing and the petrochemical industry, seeking appropriate materials with prominent performance is a crucial task and also remains an enduring challenge. To pursue this target, we report a robust microporous metal-organic framework (NUM-15) featuring two types of elaborate tri-mural nanotraps, in which fruitful nano-space confinement for accommodating gas molecules and multiple preferential adsorption sites providing multiple specific interactions with C2H2 were supplied to form cooperative effect for efficient separation property. The NUM-15a (activated NUM-15) exhibits high loading for C2H2 (3.5 mmol g−1) over carbon dioxide (CO2) and ethylene (C2H4) at 298 K and 1.0 bar and shows efficient separation performance for binary C2H2/CO2 and C2H2/C2H4 mixtures. The GCMC calculation revealed the crucial role of the multiple interactions in nanotraps for the selective capture of C2H2. Under ambient conditions, dynamic breakthrough experiments revealed that NUM-15a demonstrates the enormous potential for actual industrial gas separation and is expected to be applied to the correlative industrial process. Both experiments and simulation calculations distinctly demonstrated that fabricating tri-mural nanotraps in MOFs is a feasible strategy for efficient C2H2 capture and separation and provided a new route for exploiting high-performance materials for separation and purification technology.