Symmetry Engineering of Metal-Organic Frameworks via Ligand Desymmetrization Design for Acetylene Purification.

High-purity acetylene (C2H2) is an important chemical feedstock, yet removing the unavoidable acidic impurity carbon dioxide (CO2) remains energy-intensive using conventional methods. Metal-organic frameworks (MOFs), with tunable pore structures and abundant active sites, have attracted considerable attention for C2H2/CO2 separation. However, most reported MOFs struggle to simultaneously achieve high adsorption capacity and selectivity. In this work, ligand desymmetrization combined with a mixed-ligand strategy was employed to modulate framework symmetry, leading to the construction of two Cu-based MOFs (ZJNU-501 and ZJNU-502) with distinct pore architectures. ZJNU-501, with lower symmetry, preserves a higher density of open metal sites (OMSs) and more complex pore environments. As a result, it exhibits a C2H2 uptake of 118 cm3 g-1 at 298 K and a C2H2/CO2 selectivity of 3.2. Dynamic breakthrough experiments show that ZJNU-501 can produce C2H2 with a purity of 99.5% at a productivity of 1.33 mol kg-1 under ambient conditions, together with good cycling stability. In contrast, ZJNU-502 shows moderate performance due to its higher symmetry and reduced OMS density. This work not only confirms the potential of using the ligand desymmetrization strategy in constructing complex pore structures but also demonstrates the application of such materials in addressing energy-critical separation technologies.