Zirconium based metal–organic framework UiO-66 is to date considered one of the benchmark compounds among stable MOFs, and it has attracted huge attention for its employment in many strategic applications. Large scale production of UiO-66 for industrial purposes requires the use of safe and green solvents, fulfilling the green chemistry principles and able to replace the use of N,N-dimethylformamide (DMF), which, despite its toxicity, is still considered the most efficient solvent for obtaining UiO-66 of high quality. Herein we report on a survey of about 40 different solvents with different polarities, boiling points and acidities, used for the laboratory scale synthesis of high quality UiO-66 crystals. The solvents were chosen according to the European REACH Regulation 1907/2006 among those having a low cost and low toxicity and being fully biodegradable. Concerning MOF synthesis, the relevant parameters chosen for establishing the quality of the results obtained are the degree of the crystallinity, microporosity, specific surface area, yield, and solvent recyclability. Taking into account also the chemical physical properties of all the solvents, a color code was assigned in order to give a final green assessment for the UiO-66 synthesis. Defectivity of the obtained products, the use of acidic modulators, and the use of alternative Zr salts have been also taken into consideration. Preliminary results lead to the conclusion that GVL (γ-valerolactone) is among the most promising solvents for replacing DMF in UiO-66 MOF synthesis.

中文翻译：

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广泛筛选安全可持续的UiO-66合成用绿色溶剂

迄今为止，基于锆的金属有机框架UiO-66被认为是稳定MOF中的基准化合物之一，并且因其在许多战略应用中的使用而引起了极大的关注。为了工业目的大规模生产UiO-66，需要使用安全的绿色溶剂，符合绿色化学原理，并且能够替代N，N-二甲基甲酰胺（DMF），尽管具有毒性，但仍被认为是获得高质量UiO-66的最有效溶剂。在这里，我们报告了对大约40种具有不同极性，沸点和酸度的不同溶剂的调查，这些溶剂用于实验室规模的高质量UiO-66晶体合成。根据欧洲REACH法规1907/2006，选择具有低成本，低毒性且可完全生物降解的溶剂。关于MOF合成，为确定获得的结果的质量而选择的相关参数是结晶度，微孔率，比表面积，产率和溶剂可回收性。还考虑到所有溶剂的化学物理性质，分配了颜色代码，以便对UiO-66合成进行最终的绿色评估。还考虑了所得产物的缺陷性，使用酸性调节剂和使用替代的Zr盐。初步结果得出结论，GVL（γ-戊内酯）是取代UiO-66 MOF合成中DMF的最有希望的溶剂之一。