Jia-Le Lin, Ze-Kun Wang, Zi-Yue Xu, Lei Wei, Yun-Chang Zhang,* Hui Wang, Dan-Wei Zhang, Wei Zhou, Yue-Biao Zhang, Yi Liu,* and Zhan-Ting Li*
 J. Am. Chem. Soc. 2020142, 3577–3582
Four water-soluble hydrazone-based three-dimensional (3D) flexible organic frameworks FOF-1–4 have been synthesized from a semirigid tetracationic tetraaldehyde and four flexible dihydrazides. 1H NMR spectroscopy indicated the quantitative formation of FOF-1–4 in D2O, while dynamic light scattering experiments revealed that, depending on the concentration, these porous frameworks display hydrodynamic diameters ranging from 50 to 120 nm. The porosity of the frameworks is confirmed by ethanol vapor adsorption experiments of the solid samples as well as the high loading capacity for a 2.3 nm porphyrin guest in water. The new water-soluble frameworks exhibit low cytotoxicity and form inherent pores with diameters of 5.3 or 6.7 nm, allowing rapid inclusion of proteins such as bovine serum albumin and green and orange fluorescent proteins, and efficient delivery of the proteins into normal and cancer cells. Flow cytometric analysis reveals percentages of the delivered cells up to 99.8%.