Department of Chemistry, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, United States.
J Am Chem Soc. 2021 Jan 20;143(2):1107-1118. doi: 10.1021/jacs.0c11920. Epub 2021 Jan 7.
Artificial enzymatic systems are extensively studied to mimic the structures and functions of their natural counterparts. However, there remains a significant gap between structural modeling and catalytic activity in these artificial systems. Herein we report a novel strategy for the construction of an artificial binuclear copper monooxygenase starting from a Ti metal-organic framework (MOF). The deprotonation of the hydroxide groups on the secondary building units (SBUs) of MIL-125(Ti) (MIL = Matériaux de l'Institut Lavoisier) allows for the metalation of the SBUs with closely spaced Cu pairs, which are oxidized by molecular O to afford the Cu(μ-OH) cofactor in the MOF-based artificial binuclear monooxygenase . An artificial mononuclear Cu monooxygenase was also prepared for comparison. The MOF-based monooxygenases were characterized by a combination of thermogravimetric analysis, inductively coupled plasma-mass spectrometry, X-ray absorption spectroscopy, Fourier-transform infrared spectroscopy, and UV-vis spectroscopy. In the presence of coreductants, exhibited outstanding catalytic activity toward a wide range of monooxygenation processes, including epoxidation, hydroxylation, Baeyer-Villiger oxidation, and sulfoxidation, with turnover numbers of up to 3450. showed a turnover frequency at least 17 times higher than that of . Density functional theory calculations revealed O activation as the rate-limiting step in the monooxygenation processes. Computational studies further showed that the Cu sites in cooperatively stabilized the Cu-O adduct for O-O bond cleavage with 6.6 kcal/mol smaller free energy increase than that of the mononuclear Cu sites in , accounting for the significantly higher catalytic activity of over .
人工酶系统被广泛研究，以模拟其天然对应物的结构和功能。然而，在这些人工系统中，结构建模和催化活性之间仍然存在显著差距。本文报道了一种从 Ti 金属有机骨架 (MOF) 构建人工双核铜单加氧酶的新策略。MIL-125(Ti)（MIL = Matériaux de l'Institut Lavoisier）的次级结构单元 (SBU) 上的氢氧根去质子化允许 SBU 与紧密间隔的 Cu 对进行金属化，这些 Cu 对被分子 O 氧化，在 MOF 基人工双核单加氧酶中提供 Cu(μ-OH)辅因子。还制备了一种人工单核 Cu 单加氧酶用于比较。MOF 基单加氧酶通过热重分析、电感耦合等离子体质谱、X 射线吸收光谱、傅里叶变换红外光谱和紫外可见光谱进行了表征。在核心还原剂的存在下， 对广泛的单加氧过程表现出出色的催化活性，包括环氧化、羟基化、Baeyer-Villiger 氧化和砜氧化，转化率高达 3450。 比 显示出至少 17 倍的周转率频率更高。密度泛函理论计算表明 O 活化是单加氧过程中的速率限制步骤。计算研究进一步表明， 在 中，Cu 位点协同稳定了 Cu-O 加合物，用于 O-O 键断裂，自由能增加比单核 Cu 位点小 6.6 kcal/mol，这解释了 比 具有更高的催化活性。
