Liu Huan, Li Jialu, Liang Xiao, Ren Hongyuan, Yin Hang, Wang Ligang, Yang Da, Wang Dingsheng, Li Yadong
Department of Chemistry, Tsinghua University, Beijing 100084, P. R. China.
State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian 116023, P. R. China.
J Am Chem Soc. 2024 Aug 28;146(34):24033-24041. doi: 10.1021/jacs.4c07674. Epub 2024 Aug 15.
Palladium (Pd)-based single-atom catalysts (SACs) have shown outstanding selectivity for semihydrogenation of alkynes, but most Pd single sites coordinated with highly electronegative atoms (such as N, O, and S) of supports will result in a decrease in the electron density of Pd sites, thereby weakening the adsorption of reactants and reducing catalytic performance. Constructing a rich outer-shell electron environment of Pd single-atom sites by changing the coordination structure offers a novel opportunity to enhance the catalytic efficiency with excellent alkene selectivity. Therefore, in this work, we first propose the in situ preparation of isolated Pd sites encapsulated within Al/Si-rich ZSM-5 structure using the one-pot seed-assisted growth method. Pd@ZSM-5 features Pd-O-Al/Si bonds, which can boost the domination of d-electron near the Fermi level, thereby promoting the adsorption of substrates on Pd sites and reducing the energy barrier for the semihydrogenation of alkynes. In semihydrogenation of phenylacetylene, Pd@ZSM-5 catalyst performs the highest turnover frequency (TOF) value of 33582 mol/mol/h with 96% selectivity of styrene among the reported heterogeneous catalysts and nearly 17-fold higher than that of the commercial Lindlar catalyst (1992 mol/mol/h). This remarkable catalytic performance can be retained even after 6 cycles of usage. Particularly, the zeolitic confinement structure of Pd@ZSM-5 enables precise shape-selective catalysis for alkyne reactants with a size less than 4.3 Å.
钯（Pd）基单原子催化剂（SACs）在炔烃半加氢反应中表现出出色的选择性，但大多数与载体中高电负性原子（如N、O和S）配位的Pd单中心会导致Pd中心的电子密度降低，从而削弱反应物的吸附并降低催化性能。通过改变配位结构构建富含外壳电子的Pd单原子位点环境，为提高催化效率并具有优异的烯烃选择性提供了新的契机。因此，在本工作中，我们首次提出使用一锅种子辅助生长法原位制备封装在富含Al/Si的ZSM-5结构中的孤立Pd位点。Pd@ZSM-5具有Pd-O-Al/Si键，可增强费米能级附近d电子的主导作用，从而促进底物在Pd位点上的吸附并降低炔烃半加氢的能垒。在苯乙炔的半加氢反应中，Pd@ZSM-5催化剂在已报道的多相催化剂中表现出最高的周转频率（TOF）值，为33582 mol/mol/h，苯乙烯选择性为96%，比商业林德拉催化剂（1992 mol/mol/h）高出近17倍。即使在使用6个循环后，这种卓越的催化性能仍可保持。特别地，Pd@ZSM-5的沸石限域结构能够对尺寸小于4.3 Å的炔烃反应物进行精确的形状选择性催化。
