Co₂ and Co₃ Mixed Cluster Secondary Building Unit Approach toward a Three-Dimensional Metal-Organic Framework with Permanent Porosity.

Large and permanent porosity is the primary concern when designing metal-organic frameworks (MOFs) for specific applications, such as catalysis and drug delivery. In this article, we report a MOF Co(BTB)₆(NO₃)₄(DEF)₂(H₂O) (, H₃BTB = 1,3,5-tris(4-carboxyphenyl)benzene; DEF = ,-diethylformamide) via a mixed cluster secondary building unit (SBU) approach. MOF is sustained by a rare combination of a linear trinuclear Co₃ and two types of dinuclear Co₂ SBUs in a 1:2:2 ratio. These SBUs are bridged by BTB ligands to yield a three-dimensional (3D) non-interpenetrated MOF as a result of the less effective packing due to the geometrically contrasting SBUs. The guest-free framework of has an estimated density of 0.469 g cm and exhibits a potential solvent accessible void of 69.6% of the total cell volume. The activated sample of exhibits an estimated Brunauer-Emmett-Teller (BET) surface area of 155 m² g and is capable of CO₂ uptake of 58.61 cm³ g (2.63 mmol g, 11.6 wt % at standard temperature and pressure) in a reversible manner at 195 K, showcasing its permanent porosity.