Plascencia Cesar, Curtiss Larry A, Liu Cong
Materials Science Division , Argonne National Laboratory , 9700 South Cass Avenue , Lemont Illinois 60439 United States.
Department of Chemistry , Michigan State University , 220 Trowbridge Road , East Lansing , Michigan 48824 United States.
J Phys Chem A. 2019 Jan 10;123(1):171-186. doi: 10.1021/acs.jpca.8b08340. Epub 2018 Dec 20.
Single-site heterogeneous catalysts (SSHC) have received increasing attention due to their well-defined active sites and potentially high specific activity. Detailed computational studies were carried out on a set of potential SSHC's, i.e., silica-supported metal ions, to investigate the reactivity of these catalysts with H as well as to evaluate the performance of density functional theory (DFT) methods in conjunction with triple-ζ quality basis sets (i.e., cc-pVTZ) on reaction energetics. The ions considered include 4d and 5d metals as well as several post-transition metal ions. A representative cluster model of silica is used to calculate reaction free energies of the metal hydride formation that results from the heterolytic cleavage of H on the M-O bond. The hydride formation free energy is previously shown to be strongly correlated with the catalytic activity of such catalysts for alkene hydrogenation. ONIOM calculations (CCSD(T)//MP2) are used to assess the accuracy and reliability of the MP2 results and it is found that MP2 is a suitable level of theory for gauging the performance of DFT functionals. The performance of various DFT functionals is assessed relative to MP2 results and it is found that the wB97xd and PBE0 functionals have the lowest standard deviation (STD) value while the MN12SX and PBE functionals have the lowest mean absolute deviation (MAD) values. The B3LYP functional is shown to have similar MAD and STD values as the top performing functionals. Potential active SSHC's for exergonic hydrogen activation predicted in this study include mostly late and post transition metal ions, i.e., Au, Pd, Pt, Pd, Ir, Hg, Rh, Pb, Tl, In, Ir, Os, Cd, Ru, and Ga. This study provides important guidance to future computational studies of such catalyst systems.
单中心非均相催化剂（SSHC）因其明确的活性位点和潜在的高比活性而受到越来越多的关注。对一组潜在的SSHC，即二氧化硅负载的金属离子，进行了详细的计算研究，以研究这些催化剂与H的反应活性，并结合三重ζ质量基组（即cc-pVTZ）评估密度泛函理论（DFT）方法在反应能量学方面的性能。所考虑的离子包括4d和5d金属以及几种后过渡金属离子。使用二氧化硅的代表性簇模型来计算由于H在M-O键上的异裂而形成金属氢化物的反应自由能。先前已表明氢化物形成自由能与这类催化剂对烯烃加氢的催化活性密切相关。使用ONIOM计算（CCSD(T)//MP2）来评估MP2结果的准确性和可靠性，发现MP2是衡量DFT泛函性能的合适理论水平。相对于MP2结果评估了各种DFT泛函的性能，发现wB97xd和PBE0泛函具有最低的标准偏差（STD）值，而MN12SX和PBE泛函具有最低的平均绝对偏差（MAD）值。结果表明，B3LYP泛函的MAD和STD值与表现最佳的泛函相似。本研究预测的用于放能氢活化的潜在活性SSHC大多包括晚期和后过渡金属离子，即Au、Pd、Pt、Pd、Ir、Hg、Rh、Pb、Tl、In、Ir、Os、Cd、Ru和Ga。本研究为这类催化剂体系未来的计算研究提供了重要指导。
