Exploring the environmentally friendly and low-cost synthesis strategies of phthalocyanine (Pc) crystals in just one step is an absolute challenge. The solvothermal synthesis of phthalocyanine crystals shows the advantages of high-quality crystalline products, facile reaction and purification, and low cost. Nevertheless, only a few metal phthalocyanine crystals have been successfully synthesized via solvothermal reactions. In this study, we found that the crystalline β metal-free phthalocyanine needles could be directly prepared via the tetrapolymerization of phthalodinitrile catalyzed by DBU in solvothermal reactions. Similar to the preparation of β-phthalocyanine crystals, the α metal-free phthalocyanine crystals with the specific multiply-laminated structures can be obtained through solvothermal reactions assisted by DBN. SEM characterization showed that the individual β metal-free phthalocyanine has a well-defined quadrangular shape with smooth faces. However, the α metal-free phthalocyanine exhibits a distinctive undulating surface morphology. Both phthalocyanines showed satisfactory thermal stability (from room temperature to about 300 °C), excellent resistance to acid/alkali solution, and fast photoelectric response properties (order of magnitude of response time, 10⁻⁶ s) as tested by TG-DSC and TPV, respectively. It is noted that ethanol was used as the reaction medium and the resulting phthalocyanine crystals can be facilely purified using hot ethanol to dissolve the impurities adsorbed on the surfaces of phthalocyanine crystals. Compared to the traditional methods, no re-crystallization operation was carried out for our method. To the best of our knowledge, this is the first report on the solvothermal synthesis of metal-free phthalocyanine crystals with controllable crystal form adjusted by DBU/DBN in one step.

中文翻译：

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一种通过简单溶剂热法制备结构可控的无金属酞菁晶体的绿色途径

一步探索酞菁（Pc）晶体的环保低成本合成策略是一项绝对挑战。溶剂热合成酞菁晶体具有结晶产物质量好、反应纯化容易、成本低廉等优点。然而，只有少数金属酞菁晶体已通过溶剂热反应成功合成。在这项研究中，我们发现结晶 β 无金属酞菁针可以通过以下方法直接制备DBU在溶剂热反应中催化苯二甲腈的四聚反应。与β-酞菁晶体的制备类似，在DBN辅助下通过溶剂热反应可以得到具有特定多层结构的无α金属酞菁晶体。SEM 表征表明，单个不含金属的 β 酞菁具有轮廓分明的四边形，表面光滑。然而，不含α金属的酞菁表现出独特的起伏表面形态。两种酞菁均表现出令人满意的热稳定性（从室温到约 300 °C）、优异的耐酸碱溶液和快速的光电响应特性（响应时间数量级，10 ^-6s) 分别由 TG-DSC 和 TPV 测试。值得注意的是，使用乙醇作为反应介质，所得到的酞菁晶体可以很容易地使用热乙醇进行纯化，以溶解吸附在酞菁晶体表面的杂质。与传统方法相比，我们的方法没有进行重结晶操作。据我们所知，这是第一篇关于溶剂热合成无金属酞菁晶体的报告，该晶体具有可控的晶型，由 DBU/DBN 一步调整。