Tuning MOF Stability and Porosity via Adding Rigid Pillars

High stability and permanent porosity are the premise of general applicability for metal organic framework materials (MOFs). By varying degrees of success on increasing the connectivity of the linear pillar 4,4'-bipyridine (bpy), two isostructural flexible frameworks [M-2(obb)(2)(DMF)(2)]center dot 2DMF (1, M = Zn or Cu; H(2)obb = 4,4'-oxybis(benzoic acid), DMF = N,N-dimethylformamide) with no gas sorption are structurally modified into two rigid frameworks [Zn-2(obb)(2)(bpy)]center dot DMF (2) and [Cu-2(obb)(2)(bpy)(0.5)(DMF)]center dot 2DMF (3) with notable gas sorption and separation properties. Especially for 3, it exhibits gas selective uptake for the adsorption of CO2 over N-2 and CH4 under 273 K and has an interesting physically lock effect in benzene and cyclohexane sorption. The results provide a successful strategy on tuning framework stability of flexible structures via adding rigid pillars.