Metal–Organic Polymers Containing Discrete Single-Walled Nanotube as a Heterogeneous Catalyst for the Cycloaddition of Carbon Dioxide to Epoxides

The
cycloaddition of carbon dioxide to epoxides to produce cyclic
carbonates is quite promising and does not result in any side products.
A discrete single-walled metal–organic nanotube was synthesized
by incorporating a tetraphenyl-ethylene moiety as the four-point connected
node. The assembled complex has a large cross-section, with an exterior
wall diameter of 3.6 nm and an interior channel diameter of 2.1 nm.
It features excellent activity toward the cycloaddition of carbon
dioxide, with a turnover number of 17,500 per mole of catalyst and
an initial turnover frequency as high as 1000 per mole of catalyst
per hour. Only minimal decreases in the catalytic activity were observed
after 70 h under identical reaction conditions, and a total turnover
number as high as 35,000 was achieved. A simple comparison of relative
porous MOFs suggested that the cross-section of the channels is an
important factor influencing the transport of the substrates and products
through the channel.