Christian Matthew S, Nenoff Tina M, Rimsza Jessica M
Geochemistry Department, Sandia National Laboratories, P.O. Box 5800, Eubank Boulevard SE, Albuquerque, New Mexico 87185, United States.
Advanced Science & Technology, Sandia National Laboratories, P.O. Box 5800, Eubank Boulevard SE, Albuquerque, New Mexico 87185, United States.
J Phys Chem A. 2023 Apr 6;127(13):2881-2888. doi: 10.1021/acs.jpca.2c07751. Epub 2023 Mar 22.
Rare-earth terephthalic acid (BDC)-based metal-organic frameworks (MOFs) are promising candidate materials for acid gas separation and adsorption from flue gas streams. However, previous simulations have shown that acid gases (HO, NO, and SO) react with the hydroxyl on the BDC linkers to form protonated acid gases as a potential degradation mechanism. Herein, gas-phase computational approaches were used to identify the formation energies of these secondary protonated acid gases across multiple BDC linker molecules. Formation energies for secondary protonated acid gases were evaluated using both density functional theory (DFT) and correlated wave function methods for varying BDC-gas reaction mechanisms. Upon validation of DFT to reproduce wave function calculation results, rotated conformational linkers and chemically functionalized BDC linkers with -OH, -NH, and -SH were investigated. The calculations show that the rotational conformation affects the molecule stability. Double-functionalized BDC linkers, where two functional groups are substituted onto BDC, showed varied reaction energies depending on whether the functional groups donate or withdraw electrons from the aromatic system. Based on these results, BDC linker design must balance adsorption performance with degradation via linker dehydrogenation for the design of stable MOFs for acid gas separations.
基于稀土对苯二甲酸（BDC）的金属有机框架（MOF）是用于从烟道气流中分离和吸附酸性气体的有前途的候选材料。然而，先前的模拟表明，酸性气体（HO、NO和SO）与BDC连接体上的羟基反应形成质子化酸性气体，这是一种潜在的降解机制。在此，采用气相计算方法来确定多个BDC连接体分子上这些二级质子化酸性气体的生成能。使用密度泛函理论（DFT）和相关波函数方法，针对不同的BDC-气体反应机制，评估了二级质子化酸性气体的生成能。在验证DFT以重现波函数计算结果后，研究了旋转构象连接体以及带有-OH、-NH和-SH的化学功能化BDC连接体。计算结果表明，旋转构象会影响分子稳定性。双功能化的BDC连接体，即在BDC上取代两个官能团，其反应能量因官能团是从芳香体系供电子还是吸电子而有所不同。基于这些结果，对于设计用于酸性气体分离的稳定MOF，BDC连接体设计必须在吸附性能与通过连接体脱氢导致的降解之间取得平衡。
