Exploring the Tunability of Trimetallic MOF Nodes for Partial Oxidation of Methane to Methanol

Density
functional theory is used to study the tunability of trigonal prismatic
SBUs found in metal–organic frameworks (MOFs) such as MIL-100,
MIL-101, and PCN-250/MIL-127 of chemical composition M3+2M2+(μ3-O)­(RCOO)6 for the partial oxidation of methane to methanol. We performed a
combinatorial screening by varying the composition of the trimetallic
node (M13+)2(M22+) (where M1 and M2 = V, Cr, Mn, Fe, Co, and
Ni) and calculated the reaction pathway on both M1 and
M2 sites. The systematic replacement of metals in the trimetallic
cluster allowed us to study the influence of spectator atoms on the
catalytic activity of a specific metal site in the cluster toward
the N2O activation and C–H bond activation steps
of the reaction. In the screening, we identified the top-performing
node compositions with predicted barriers lower than those already
reported for experimentally tested MOFs with trigonal prismatic SBUs.
This work demonstrates the opportunity to tune the catalytic activity
of MOFs for redox reactions by changing their metal node composition.

本研究采用密度泛函理论（Density functional theory），针对化学组成为M³⁺₂M²⁺(μ₃-O)(RCOO)₆的三类金属有机框架（metal–organic frameworks, MOFs）——包括MIL-100、MIL-101与PCN-250/MIL-127——所包含的三角棱柱型次级结构单元（SBUs），探究其用于甲烷部分氧化制甲醇反应的可调性。我们通过调控三金属节点(M1³⁺)₂(M2²⁺)（其中M1与M2可选自V、Cr、Mn、Fe、Co及Ni）的组成开展组合筛选，并计算了M1与M2位点上的反应路径。通过系统替换三金属团簇中的金属种类，我们得以研究旁观原子对团簇中特定金属位点在该反应的一氧化二氮活化与碳氢键活化步骤中的催化活性的影响。在本次筛选中，我们鉴定出了一批性能最优的节点组成，其预测能垒低于目前已报道的、经实验验证的三角棱柱型SBUs基MOFs的对应能垒。本研究证实，可通过改变金属节点的组成来调控金属有机框架用于氧化还原反应的催化活性。