Co(2) and Co(3) 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(11)(BTB)(6)(NO(3))(4)(DEF)(2)(H(2)O)(14) (1, H(3)BTB = 1,3,5-tris(4-carboxyphenyl)benzene; DEF = N,N-diethylformamide) via a mixed cluster secondary building unit (SBU) approach. MOF 1 is sustained by a rare combination of a linear trinuclear Co(3) and two types of dinuclear Co(2) 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 1 has an estimated density of 0.469 g cm(−3) and exhibits a potential solvent accessible void of 69.6% of the total cell volume. The activated sample of 1 exhibits an estimated Brunauer-Emmett-Teller (BET) surface area of 155 m(2) g(−1) and is capable of CO(2) uptake of 58.61 cm(3) g(−1) (2.63 mmol g(−1), 11.6 wt % at standard temperature and pressure) in a reversible manner at 195 K, showcasing its permanent porosity.