Increased Electric Conductivity upon I₂ Uptake and Gas Sorption in a Pillar-Layered Metal-Organic Framework

The use of molecular iodine to tune the electrical conductivity in metal-organic frameworks is an effective but seldom investigated strategy. Herein, the single-crystal-to-single-crystal transformation of [Co_1.5 (bdc)_1.5 (H₂ bpz)]⋅DMF⋅4 H₂ O (1) to [Co_1.5 (bdc)_1.5 (H₂ bpz)]⋅0.5 I₂ ⋅DMF (I₂ @1) (H₂ bdc=1,4-benzenedicarboxylic acid, H₂ bpz=3,3',5,5'-tetramethyl-4,4'-bipyrazole) upon I₂ loading caused a three orders of magnitude enhancement in electrical conductivity of the framework. Single-crystal X-ray diffraction revealed that I₂ exists as a single molecule embedded in the channels of framework, and the C-H⋅⋅⋅I hydrogen bonds between I₂ molecules and phenyl units on the porous surface of the framework were suggested to participate in n→σ* host-guest charge transfer, leading to increased electrical conductivity in I₂ @1. Furthermore, 1 displayed moderate adsorption selectivity for CO₂ over CH₄ and N₂ .