A 3D polymorphic Cu-based ultramicroporous MOF capable of CO2 Uptake and Conversion

The development of advanced porous sorbents for CO₂ capture from gas mixtures remains pivotal for meeting net zeroemission targets by 2050. Among these, metal–organic frameworks (MOFs) continue to stand out due to their structural tunability and high surface areas. Herein, we report a new ultramicroporous 3D physisorbent MOF, constructed from CuII nodes and the multitopic 3,6-N-ditriazolyl-2,5-dihydroxy-1,4-benzoquinone anilato ligand (trz2An). This species, of [Cu(trz2An)]·nH₂O (n ≤ 3) general formula, crystallizes in two (monoclinic and orthorhombic) polymorphs. The existence of two structurally related forms arises from a polysynthetic twinning mechanism involving short range ligand reorientation within a single crystal domain. Despite such structural variability, comparative analysis of both polymorphs reveals no significant differences in porosity metrics or gas sorption behavior. [Cu(trz2An)] displays high selectivity and separation efficiency for N₂/CO₂ and CH₄/CO₂ mixtures, along with remarkable cycling stability. Furthermore, it shows promising catalytic activity toward CO₂ reduction reaction (CO₂RR), which playes a key role into carbon utilization strategies, particularly favouring the formation of ethylene — an industrially valuable product. These results highlight [Cu(trz2An)]·as a regenerable, structurally resilient MOF, combining efficient gas separation and CO₂ valorization and offering a compelling blueprint for the design of next-generation, environmentally sustainable physisorbents