Stassin Timothée, Reinsch Helge, Van de Voorde Ben, Wuttke Stefan, Medina Dana D, Stock Norbert, Bein Thomas, Ameloot Rob, De Vos Dirk
Centre for Surface Chemistry and Catalysis, KU Leuven, Celestijnenlaan 200F box 2461, 3001, Leuven, Belgium.
Institute of Inorganic Chemistry, Christian-Albrechts University Kiel, Max-Eyth Straße 2, 24118, Kiel, Germany.
ChemSusChem. 2017 Feb 8;10(3):643-650. doi: 10.1002/cssc.201601000. Epub 2016 Nov 29.
Biomass-derived lactic acid (LA) is an important platform chemical towards the sustainable production of numerous materials. However, the fermentation process currently in use is limited by the difficult recovery of the LA product from the fermentation broth and results in the generation of stoichiometric amounts of gypsum waste. Herein, we show that metal-organic frameworks (MOFs) of the UiO-66(Zr) type are effective adsorbents for the separation of LA from aqueous (buffer) solutions. These frameworks based on zirconium clusters and terephthalic acid derivatives display a tremendous uptake (up to 42 wt %) and a high affinity for LA. The latter can further be tuned by changing the hydrogen-bonding properties of the functional groups present on the organic ligand. A Rietveld refinement disclosed the specific interaction of LA with the clusters of UiO-66(Zr) and a preferential adsorption on open zirconium sites. Taking advantage of the catalytic activity of UiO-66(Zr), desorption of LA was performed in alcohols to recover up to 73 % as ester. Applied to the recovery of LA, adsorption and reactive desorption offer a direct and gypsum-free strategy as an alternative for the current multi-step process.
生物质衍生的乳酸（LA）是实现多种材料可持续生产的重要平台化学品。然而，目前使用的发酵过程受到从发酵液中回收LA产品困难的限制，并导致产生化学计量的石膏废料。在此，我们表明UiO-66(Zr)型金属有机框架（MOF）是从水（缓冲）溶液中分离LA的有效吸附剂。这些基于锆簇和对苯二甲酸衍生物的框架对LA表现出巨大的吸附量（高达42 wt %）和高亲和力。通过改变有机配体上存在的官能团的氢键性质，可以进一步调节后者。Rietveld精修揭示了LA与UiO-66(Zr)簇的特定相互作用以及在开放锆位点上的优先吸附。利用UiO-66(Zr)的催化活性，在醇中进行LA的解吸，以酯的形式回收高达73 %。应用于LA的回收，吸附和反应性解吸提供了一种直接且无石膏的策略，作为当前多步工艺的替代方案。
