Division of Molecular and Materials Simulation, Key Lab for Nanomaterials, Ministry of Education of China, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China.
ACS Nano. 2010 Jul 27;4(7):4225-37. doi: 10.1021/nn100962r.
We use the multiscale simulation approach, which combines the first-principles calculations and grand canonical Monte Carlo simulations, to comprehensively study the doping of a series of alkali (Li, Na, and K), alkaline-earth (Be, Mg, and Ca), and transition (Sc and Ti) metals in nanoporous covalent organic frameworks (COFs), and the effects of the doped metals on CO2 capture. The results indicate that, among all the metals studied, Li, Sc, and Ti can bind with COFs stably, while Be, Mg, and Ca cannot, because the binding of Be, Mg, and Ca with COFs is very weak. Furthermore, Li, Sc, and Ti can improve the uptakes of CO2 in COFs significantly. However, the binding energy of a CO2 molecule with Sc and Ti exceeds the lower limit of chemisorptions and, thus, suffers from the difficulty of desorption. By the comparative studies above, it is found that Li is the best surface modifier of COFs for CO2 capture among all the metals studied. Therefore, we further investigate the uptakes of CO2 in the Li-doped COFs. Our simulation results show that at 298 K and 1 bar, the excess CO2 uptakes of the Li-doped COF-102 and COF-105 reach 409 and 344 mg/g, which are about eight and four times those in the nondoped ones, respectively. As the pressure increases to 40 bar, the CO2 uptakes of the Li-doped COF-102 and COF-105 reach 1349 and 2266 mg/g at 298 K, respectively, which are among the reported highest scores to date. In summary, doping of metals in porous COFs provides an efficient approach for enhancing CO2 capture.
我们采用多尺度模拟方法，结合第一性原理计算和巨正则蒙特卡罗模拟，全面研究了一系列碱（Li、Na 和 K）、碱土（Be、Mg 和 Ca）和过渡（Sc 和 Ti）金属在纳米多孔共价有机骨架（COFs）中的掺杂，以及掺杂金属对 CO2 捕获的影响。结果表明，在所研究的所有金属中，Li、Sc 和 Ti 可以与 COFs 稳定结合，而 Be、Mg 和 Ca 则不能，因为 Be、Mg 和 Ca 与 COFs 的结合非常弱。此外，Li、Sc 和 Ti 可以显著提高 CO2 在 COFs 中的吸收量。然而，CO2 分子与 Sc 和 Ti 的结合能超过化学吸附的下限，因此，解吸困难。通过上述比较研究，发现 Li 是所有研究金属中 COFs 表面 CO2 捕获的最佳修饰剂。因此，我们进一步研究了 Li 掺杂 COFs 中 CO2 的吸收量。我们的模拟结果表明，在 298 K 和 1 bar 下，Li 掺杂的 COF-102 和 COF-105 的过量 CO2 吸收量分别达到 409 和 344 mg/g，分别是未掺杂的 COFs 的约 8 倍和 4 倍。随着压力增加到 40 bar，在 298 K 下，Li 掺杂的 COF-102 和 COF-105 的 CO2 吸收量分别达到 1349 和 2266 mg/g，这是迄今为止报道的最高分数之一。总之，金属在多孔 COFs 中的掺杂为增强 CO2 捕获提供了一种有效的方法。
