Increasing the CO 2 Reduction Activity of Cobalt Phthalocyanine by Modulating the σ-Donor Strength of Axially Coordinating Ligands
Increasing the CO 2 Reduction Activity of Cobalt Phthalocyanine by Modulating the σ-Donor Strength of Axially Coordinating Ligands
复制标题
通过调节轴向配位配体的β供体强度提高酞菁钴的CO 2 还原活性
DOI：
10.1021/acscatal.1c02379
复制
发表时间：
2021
期刊：
影响因子：
12.9
通讯作者：
McCrory, Charles C.
中科院分区：
文献类型：
--
作者：
Rivera Cruz, Kevin E.;Liu, Yingshuo;Soucy, Taylor L.;Zimmerman, Paul M.;McCrory, Charles C.
吡啶基部分与CoPc的轴向配位（外源性或聚-4-乙烯基吡啶聚合物内）显着增加了复合物的CO2还原反应（CO2 RR）活性。据推测，轴向协调的Co活性位点导致增加的Co dz 2轨道的能量，这增加了复杂的亲核性和促进CO2协调相比，母体CoPc复合物。Co dz 2轨道能量增加的幅度应取决于轴向配体的σ-供体强度，较强的σ-供体配体（L）将增加轴向配位的CoPc（L）的总体CO2 RR活性，反之亦然。为了验证这一点，我们研究了一系列CoPc（L）络合物，其中L的σ-供体强度是变化的。结果表明，CoPc（L）还原CO2的活性随着L的σ-供体能力的增加而增加。这些观察到的电化学活性趋势与计算得出的CO2结合能和电荷转移项作为σ-供体强度的函数相关。本研究的结果支持我们的假设，即轴向协调CoPc后观察到的CO2 RR活性增加是由于dz 2轨道的能量增加，并强调了大环MN 4基电催化剂的重要设计考虑。
Axial coordination of pyridyl moieties to CoPc (either exogenous or within poly-4-vinylpyridine polymer) dramatically increases the complex’s activity for the CO2reduction reaction (CO2RR). It has been hypothesized that axial coordination to the Co active site leads to an increase in the Co dz2orbital energy, which increases the complex’s nucleophilicity and facilitates CO2coordination compared to the parent CoPc complex. The magnitude of the energy increase in the Co dz2orbital should depend on the σ-donor strength of the axial ligand─a stronger σ-donating ligand (L) will increase the overall CO2RR activity of axially coordinated CoPc(L) and vice versa. To test this, we have studied a series of CoPc(L) complexes where the σ-donor strength of L is varied. We show that CoPc(L) reduces CO2with an increased activity as the σ-donor ability of L is increased. These observed electrochemical activity trends are correlated with computationally derived CO2binding energy and charge transfer terms as a function of σ-donor strength. The findings of this study support our hypothesis that the increased CO2RR activity observed upon axial coordination to CoPc is due to the increased energy of the dz2orbital, and highlight an important design consideration for macrocyclic MN4-based electrocatalysts.