To manage production costs and lower the conversion temperature of microalgal lipids, this study engineered superacid sites in MOF-808, facilitating lipid transformation at markedly reduced temperatures. Through simple substitution and activation steps, secondary building units formed by Zr(IV) and Ce(III) were assembled with benzene-1,3,5-tricarboxylate ligands, resulting in a unique superacid structure. This superacid structure has a Hammett acidity value of less than −14.5 and a deprotonation energy of 1016.25 kJ mol⁻¹, both lower than those of sulfuric acid. Density functional theory and solid-state NMR analyses confirmed the superacidity arises from a weakly constrained superacid proton within a bridging structure, formed by two methanol molecules attracted to adjacent Ce and Zr atoms. Variable temperature infrared spectroscopy demonstrated the low-temperature activation of methanol, with the optimal reaction temperature reduced from 200 °C to 150 °C and pressure reduced by 2952 kPa. Unlike traditional solid superacids, this methanol-based superacid configuration prevents the loss of superacid sites, maintaining over 97% efficiency after five cycles.

中文翻译：

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Zr(IV)/Ce(III) MOF-808 中的超酸性：在低温下利用微藻脂质生产生物柴油


为了控制生产成本并降低微藻脂质的转化温度，本研究在 MOF-808 中设计了超酸位点，以在显着降低的温度下促进脂质转化。通过简单的取代和活化步骤，由Zr( IV )和Ce( III )形成的二级结构单元与1,3,5-三羧酸苯配体组装在一起，形成独特的超强酸结构。该超酸结构的哈米特酸度值小于-14.5，去质子化能为1016.25 kJ mol ^-1 ，均低于硫酸。密度泛函理论和固态核磁共振分析证实，超强酸性是由桥接结构内弱约束的超强酸质子产生的，该桥接结构是由两个被相邻的 Ce 和 Zr 原子吸引的甲醇分子形成的。变温红外光谱证明了甲醇的低温活化，最佳反应温度从200℃降低至150℃，压力降低2952kPa。与传统的固体超强酸不同，这种基于甲醇的超强酸配置可防止超强酸位点的损失，在五个循环后保持超过 97% 的效率。