Increased Electric Conductivity upon I-2 Uptake and Gas Sorption in a Pillar-Layered Metal-Organic Framework

摘要

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)(H(2)bpz)]DMF4H(2)O (1) to [Co-1.5(bdc)(1.5)(H(2)bpz)]0.5I(2)DMF (I-2@1) (H(2)bdc=1,4-benzenedicarboxylic acid, H(2)bpz=3,3,5,5-tetramethyl-4,4-bipyrazole) upon I-2 loading caused a three orders of magnitude enhancement in electrical conductivity of the framework. Single-crystal X-ray diffraction revealed that I-2 exists as a single molecule embedded in the channels of framework, and the C-HI hydrogen bonds between I-2 molecules and phenyl units on the porous surface of the framework were suggested to participate in n sigma* host-guest charge transfer, leading to increased electrical conductivity in I-2@1. Furthermore, 1 displayed moderate adsorption selectivity for CO2 over CH4 and N-2.