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)]·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)]·DMF (2) and [Cu(2)(obb)(2)(bpy)(0.5)(DMF)]·2DMF (3) with notable gas sorption and separation properties. Especially for 3, it exhibits gas selective uptake for the adsorption of CO(2) over N(2) and CH(4) 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.