Nitrogen-rich heterocyclic compounds (NRHCs) are an emerging type of explosive, and their quantification is important in national security inspection and environmental monitoring. Up until now, designing an efficient NRHCs sensing strategy was still in the early stages. Herein, a new metal–organic framework (MOF) with aggregation-induced emission (AIE) characteristics is synthesized with fluorometric/colorimetric responses for rapid and selective detection of NRHCs. The nonemissive probe is designed with tetraphenylethylene derivative as the linker and Co as the node, quencher, and color-changing agent. Cobalt AIE-MOF exhibits a turn-on emission enhancement due to the competitive coordination substitution between NRHCs and the scaffold as well as the following AIE process of the liberative linkers. Meanwhile, the color appearance of the probe changes from blue to yellow based on the dissociation of the original Co coordinating system. Using this dual-mode probe, single- and dual-ring NRHCs are successfully detected from 5 μM to 7.5 mM within 25 s. The cobalt AIE-MOF exhibits excellent selectivity of NRHCs against a variety of interferences, providing a promising tool for designing a multichannel detection strategy.

Cationic metal−organic framework (MOF) materials are widely used in the anion separation field, but there are few reports of pyrimidyl ligands as building units. In this work, three new cationic MOFs based on pyrimidyl as functional group ligands were synthesized for the removal of radioactive pertechnetate from aqueous solution. The pyrimidyl ligands were designed by incorporating pyrimidyl units into the skeletons of benzene, triphenylamine, and tetraphenylethylene, respectively. Taking advantage of multiple coordination sites of pyrimidyl groups, three cationic MOFs (ZJU-X11, ZJU-X12, and ZJU-X13) with diverse structures were solvothermally synthesized using silver ion as the metal node. Scanning electron microscopy−energydispersive spectroscopy mapping demonstrated that these three cationic MOFs could capture ReO 4 − via anion exchange, but the sorption capabilities were distinctly different. With 95% removal toward ReO 4 − , ZJU-X11 showed the strongest anion-exchange competence among the three MOFs. According to the results of batch experiments, ZJU-X11 could achieve sorption equilibrium within 10 min, remove 518 mg of ReO 4− per 1 g of ZJU-X11, remove most of ReO 4 − after four recycles, and maintain satisfactory selectivity in the presence of excess competing anions, which is one of the best MOF materials for removing ReO 4 − /TcO 4 − among the three cationic MOFs. This work indicates that the pyrimidyl group is a promising multiple site to build versatile cationic MOFs.

Albeit reported substantial sorbents for elimination of TcO 4 − , the issue of secondary contamination caused by released counterions (such as NO 3 − ) from the cationic metal−organic framework (MOF) has not come into the sufficient limelight for researchers. Herein, our efforts are dedicated to settle the matter through synthesis of NiCl 2 based on the cationic MOF (ZJU-X4). Less harmful chlorides are used as exchangeable anions for replacing hazardous anions. Notably, ZJU-X4 exhibited fast sorption kinetics, high sorption capacity of 395 mg/g, decent selectivity, and excellent reusability in four recycles. The results of ion chromatography revealed that the released chloride ion was equal to sorption of target ions, and pair distribution functions were employed to analyze the changes in ZJU-X4 after sorption of ReO 4 − , clearly elucidating the anion-exchange mechanism. Furthermore, in the dynamic sorption experiments, ReO 4 − could be facilely and effectively removed and recovered, showing the value of practical applications. This work indicated that cationic MOFbased metal chloride salts would be a better choice for anionic sorbents.

Effective elimination of pertechnetate (TcO 4 − ) from nuclear waste is meaningful for decreasing the impact toward actinide separation and reducing the amount of radioactive wastewater from disposal nuclear waste. Nevertheless, construction of sorbents with the features of facile synthesis, strong acid and alkali resistance, fast sorption kinetics, and high sorption capacity remains quite challenging. In this work, cationic polymeric networks (CPN-X1-Cl and CPN-X2-Cl) based on elongated organic ligands were designed and synthesized by a facile quaternization reaction, and their sorption performance toward ReO 4− was thoroughly investigated. The plentiful pyridinium moieties endowed these cationic polymer networks with high charge density, resulting in CPN-X1-Cl achieving a maximum sorption capacity of 813 mg/g and surpassing most cationic materials. Furthermore, both CPN-X1-Cl and CPN-X2-Cl exhibited ultrafast sorption kinetics, high selectivity, and recyclability in five recycles. The sorption mechanism was clearly elucidated by XPS, FT-IR, ion chromatography, and DFT calculations, revealing the process of anion exchange, sorption geometry, and binding energy. In addition, in the dynamic sorption experiments, CPN-X1-Cl as a filler could effectively remove ReO 4 − , showing impressive practical application ability in disposal of radioactive waste. This work indicated that the CPNs with elongated ethynyl-based ligands had tremendous potential as radioactive TcO 4 − scavengers.

In the field of replacement of conventional dialysis treatment, searching superior materials for removal of protein-bound uremic toxins is a challenge on account of strong interactions between proteins and uremic toxins. Herein, we first adopted cationic metal−organic frameworks (MOFs), ZJU-X6 and ZJU-X7, as sorbents to decontaminate uremic toxins (p-cresyl sulfate and indoxyl sulfate). ZJU-X6 and ZJU-X7 exhibited innate advantage for sequestration of uremic toxins by utilizing a positive charge framework with exchangeable anions. Especially, ZJU-X6 showed a higher sorption capacity and faster sorption kinetics than those of most reported materials. Moreover, the cationic MOF materials could selectively remove uremic toxins even if in the presence of competitive chloride ions and proteins. Meanwhile, pair distribution function (PDF) and density functional theory (DFT) were employed to elucidate the sorption mechanism between uremic toxins and sorbents. This work suggests an attractive avenue for constructing new types of sorbents to eliminate uremic toxins for uremia treatment.