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.

将二氧化碳与环氧化物进行环加成反应以制备环状碳酸酯，该合成路径极具应用前景且无副产物生成。本研究通过引入四苯乙烯基团作为四连接节点，合成了一种离散型单壁金属有机纳米管（discrete single-walled metal–organic nanotube）。该组装配合物具有较大的截面尺寸，外壁直径达3.6 nm，内部通道直径为2.1 nm。该材料对二氧化碳环加成反应表现出优异的催化活性，每摩尔催化剂的转化数（turnover number, TON）可达17500，初始转化频率（turnover frequency, TOF）最高可达每小时每摩尔催化剂1000。在相同反应条件下连续反应70小时后，其催化活性仅出现极小幅度的下降，总转化数最高可达35000。通过对相关多孔金属有机框架材料（metal-organic frameworks, MOFs）的简单对比分析可知，通道截面尺寸是影响底物与产物在通道内传输的重要因素。