Dynamic weak coordination bonding of chlorocarbons enhances the catalytic performance of a metal-organic framework material

Abstract

Coordination bondings have shown their critical roles in various inorganic reactions after Alfred Werner; however, it remains challenging to find extremely weak coordination bonding due to the difficulties in characterizing it with conventional analytical techniques. Here we present the Lewis basicity of chlorocarbons, i.e., trichloromethane and dichloromethane, that possess lone-pair electrons on their neutral chlorine atoms and their ability to form dynamic weak coordination bonding. A paddlewheel Cu-3(BTC)(2) metal-organic framework confining trichloromethane (TCM) in the pores reveals the ability of TCM to form dynamic weak coordination bonding and coordinative equilibrium with relatively stronger Lewis basic solvents such as water, methanol, or ethanol at the axial open Cu(ii) site. However, trichloromethane differs from dichloromethane in coordination strength despite their structural similarity. By examining the catalytic hydrogenation reaction of acetophenone and acetone with activated Cu-3(BTC)(2), further, we show that solvents with dynamic weak coordination bonding can give rise to higher efficiencies in catalytic reactions than those with strong coordination bonding.