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 [Co1.5 (bdc)1.5 (H2 bpz)]⋅DMF⋅4 H2 O (1) to [Co1.5 (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 .