A cationic COF removes carcinogenic bromate with a remarkable rate constant of 191.45 g mg⁻¹ min⁻¹.

Herbicide paraquat (dimethylviologen) is a major water pollutant threatening ecosystems and human health. Therefore, it is crucial to develop materials to remove it from water. Three calix[n]arene-based (n = 4, 6, 8) porous organic polymers with different cavity sizes of the backbone macrocycle (CX4P, CX6P, CX8P) were synthesized and tested for their potential use in toxic paraquat removal. These polymers reached some of the highest reported maximum uptake capacities (Q_max up to 419 mg g⁻¹) and showed high adsorption rate constants (k_obs up to 0.179 g mg⁻¹ min⁻¹). Importantly, the materials could be easily regenerated by simple washing methods and reused without significant losses in their efficiency while still outperforming commercial activated carbon currently used in water purification.

Fluorescent covalent organic frameworks (COFs) are promising candidates for imaging living cells due to their unique properties. Herein, we critically reviewed the progress and structure–activity relations of COFs for the effective bioimaging.

Azacalix[n]arenes (ACAs) are lesser-known cousins of calix[n]arenes that contain amine bridges instead of methylene bridges, so they generally have higher flexibility due to enlarged cavities. Herein, we report a highly substituted cationic azacalix[4]arene-based covalent organic framework (ACA-COF) synthesized by the Zincke reaction under microwave irradiation. The current work is a rare example of a synthetic strategy that utilizes the chemical functionalization of an organic macrocycle to constrain its conformational flexibility and, thereby, produce an ordered material. Considering the ACA cavity dimensions, and the density and diversity of the polar groups in ACA-COF, we used it for adsorption of uric acid and creatinine, two major waste products generated during hemodialysis treatment in patients with renal failure. This type of application, which has the potential to save ∼400 L of water per patient per week, has only been recognized in the last decade, but could effectively address the problem of water scarcity in arid areas of the world. Rapid adsorption rates (up to k = 2191 g mg^-1 min^-1) were observed in our COF, exceeding reported values by several orders of magnitude.

Global consumption and discharge of palladium (Pd) have raised environmental concerns but also present an opportunity for the sustainable recovery and reuse of this precious metal. Adsorption has proven to be an efficient method for the selective recovery of Pd from industrial wastewater. This study investigated a hydrazone-linked covalent organic framework (Tfpa-Od COF) as a potential material for the high-affinity adsorption of Pd²⁺ ions from wastewater, achieving a K_d value of 3.62 × 10⁶ mL g^-1. The electron-rich backbone of the COF contributes to its excellent selective removal efficiency (up to 100%) and adsorption capacity of 372.59 mg g^-1. Furthermore, the Pd-adsorbed COF was evaluated as a sustainable catalyst for the Suzuki-Miyaura coupling reaction, demonstrating good catalytic conversion and recyclability. This work attempts to showcase a protocol for reusing waste palladium generated in water to fabricate heterogeneous catalysts and, thereby, promote the circular economy concept.