Directing Reaction Pathways on Supported Metal Catalysts with Low-Density Self-Assembled Monolayers
Directing Reaction Pathways on Supported Metal Catalysts with Low-Density Self-Assembled Monolayers
复制标题
DOI：
10.1021/acsanm.3c01836
复制
发表时间：
2023-05
影响因子：
5.9
通讯作者：
Zachary Blanchette;D. K. Schwartz;J. Medlin
中科院分区：
文献类型：
--
作者：
Zachary Blanchette;D. K. Schwartz;J. Medlin
控制反应物在催化剂表面上的吸附对于反应活性和选择性至关重要。一种用于改善选择性的方法是通过施加空间约束以使反应物结合取向偏置。在这项研究中，硫醇自组装单分子膜（SAMs）沉积到Pt/Al 2 O3催化剂作为一种方法来控制活性和选择性通过空间效应。除了完整的单层之外，还采用了低密度SAM涂覆的催化剂。一些表征技术证明了成功的沉积均匀的低密度自组装膜的金属表面上减少网站阻塞相比，一个完整的高密度单层。反应动力学研究表明，增加苯甲醇加氢脱氧（HDO）的选择性SAM改性的催化剂。这是由于反应物不能吸附在芳环平行于表面的催化剂上，从而阻止了脱羰和环加氢反应途径。此外，SAM密度影响反应活性显着，与低密度改性的SAM催化剂是更积极的比催化剂涂覆有一个完整的单层。此外，液相加氢反应被用来研究SAM密度和反应性之间的关系，为各种大小的反应物分子。在所有情况下，低密度SAM相对于致密SAM提高了反应速率。控制配体密度的效果取决于反应的类型：高配体密度大大减少了环氢化，而HDO在很大程度上不受影响，这表明一个潜在的策略，大小选择性的反应速率和选择性控制。
Controlling reactant adsorption on catalyst surfaces is crucial to reaction activity and selectivity. One method for improving selectivity is by imposing steric constraints to bias the reactant binding orientation. In this study, thiol self-assembled monolayers (SAMs) were deposited onto Pt/Al2O3catalysts as a method for controlling activity and selectivity via steric effects. In addition to a full monolayer, a low-density SAM-coated catalyst was employed. A number of characterization techniques demonstrated the successful deposition of homogeneous low-density SAMs on the metal surface with reduced site-blocking compared to a full high-density monolayer. Reaction kinetic studies showed increased benzyl alcohol hydrodeoxygenation (HDO) selectivity for both SAM-modified catalysts. This was attributed to the inability of the reactant to adsorb on the catalyst with the aromatic ring parallel to the surface, thus preventing decarbonylation and ring hydrogenation reaction pathways. Additionally, SAM density influenced reaction activity significantly, with the low-density-modified SAM catalyst being more active than the catalyst coated with a full monolayer. Moreover, liquid-phase hydrogenation reactions were used to investigate the relationship between SAM density and reactivity for reactant molecules of various sizes. In all cases, the low-density SAM improved reaction rates relative to dense SAMs. The effect of controlling ligand density depended on the type of reaction: high ligand densities greatly diminished ring hydrogenation, while HDO was largely unaffected, suggesting a potential strategy for size-selective reaction rate and selectivity control.