Manipulation of Amorphous-to-Crystalline Transformation: Towards the Construction of Covalent Organic Framework Hybrid Microspheres with NIR Photothermal Conversion Ability

An approach to transforming amorphous organic networks into crystalline covalent organic frameworks (COFs) with retention of the colloidal nanosize and uniform morphology is presented. Specifically, Fe3O4 nanoclusters are encapsulated by a disordering polyimine network via the Schiff-base reaction. The formed imine bonds could be reconstructed under thermodynamic control to reform the polyimine networks into imine-linked COFs insitu. Such a core-shell microsphere exhibits the uniform size and spherical shape, controllable COF shell thickness, accessible surface modification, and improved solution dispersibility as well as maintenance of high surface area, periodic micropores, and superior magnetic responsiveness. Additionally, the photothermal conversion effect is demonstrated for the first time on the nanoCOF layers upon exposure to near infrared light, providing convincing evidence for potential use in phototherapy.

提出了一种在保持胶体纳米尺寸和均匀形貌的情况下将无定形有机网络转化为结晶共价有机框架（COFs）的方法。具体而言，通过席夫碱反应，四氧化三铁纳米团簇被无序的聚亚胺网络包裹。形成的亚胺键可在热力学控制下重构，从而将聚亚胺网络原位重构成亚胺连接的COFs。这种核 - 壳微球具有尺寸均匀、球形形状、可控的COF壳层厚度、可进行表面修饰、溶液分散性提高以及保持高比表面积、周期性微孔和优异的磁响应性等特点。此外，首次在近红外光照射下在纳米COF层上展示了光热转换效应，为其在光疗中的潜在应用提供了有力证据。