Search

Graphical abstract Abstract In this study, we prepared a hydrothermal carbon-based supramolecular organic framework (HTC-MA-TMA) by grafting melamine and trimesic acid on hydrothermal carbon (HTC) for efficient removal of U (VI) from aqueous solutions. The nano-sized supramolecular organic framework (SOF) particles consisted of N-donor-containing melamine and O-donor-containing trimesic acid self-assembled through hydrogen bonds. Their large number of specific active sites acted as the immobilization center for capturing U (VI). Chemical modification facilitated the dispersion of the SOF particles on HTC, which was synthesized using a novel covalent/non-covalent bond strategy. The HTC-MA-TMA adsorbent exhibited exceptional U (VI) adsorption capacity (271.83 mg/g) because of the coordination interaction between UO 2 2+ and its ligands (amino, carboxyl and amide groups). The adsorption equilibrium was achieved within 30 min and followed a pseudo-second-order equation, suggesting the occurrence of a chemical adsorption process. Furthermore, the U (VI) ions adsorbed onto the HTC-MA-TMA adsorbent could be easily desorbed using 0.1 M HNO 3 solution. This regeneration caused no significant decrease in the sorption capacity of the adsorbent. These results suggest that advanced HTC-MA-TMA adsorbent can be applied in the nuclear-fuel industry for extracting U (VI) from radioactive wastewater. [ABSTRACT FROM AUTHOR]

• A novel hierarchical cubic Li x TiO 2 -based hollow Li-ion sieve was constructed. • A prelithiation concept at a mild temperature is proposed to engineer active Li+ sites. • ZIF-8 with unique 6-ring window is employed as Li+ channel for selective recovery. • The hollow TiO 2 -based core–shell hybrid yields high Li+ capture capacity against competing ions. Sustainable lithium supply significantly matters the healthy development of electric vehicles markets. Selective adsorption plays an important role in aqueous lithium recovery due to low energy consumption and easy processing. We here report a prelithiation concept to generate active Li+ sites in TiO 2 forming Li x TiO 2 at a mild temperature for lithium recovery. A hollow protonated Li x TiO 2 matrix with nanosheets surface was built to provide abundant active sites for specific Li+ capture with fast matter transfer. And a biomimetic metal–organic framework (ZIF-8) gate layer, acting as Li+ channel, was engineered to regulate cation solvation structure for selective transport of Li+. Consequently, the resultant TiO 2 -based hybrid lithium-ion sieve demonstrates fast and homogenous Li+ chemisorption with a high Li+ uptake capacity (∼14 mg g−1 for 24 h at pH = 12), high Li+ selectivity against competing cations in both simulated and natural brine, and acceptable reusability in simulated brine, indicating further application potential. [ABSTRACT FROM AUTHOR]

A series of Ag-modified MOF/SOF heterostructured framework adsorbents (Ag-MSHC) with strong binding of iodine were prepared by anchoring silver nanoclusters on MOF/SOF heterostructured framework (MSHC). Morphological transformation process of six novel Ag-MSHC adsorbents can be realized by tailoring the molar ratio of Fe3+, TMA (1,3,5-Tricarboxybenzen) and MA (melamine), finally resulting in a combination of MOFs (metal−organic frameworks) and SOFs (supramolecular organic framework). Among six adsorbents, Ag-MSHC-6 exhibited an extremely strong affinity towards I−, whereas the maximum adsorption capacity of I− reaches 771.6 mg/g. An increased tendency of I− sorption occurred from Ag-MSHC-1 to Ag-MSCH-6 when the molar ratio of Fe3+ gradually decreased because the content of Fe3+ in topological structure of Ag-MSHC can hinder the incorporation of silver nanoclusters into Ag-MSHC and further influences the irreversible interactions between Ag 2 O and I−. Besides, FT-IR, XPS, TGA and SEM were used to discuss the microstructures and chemical composition of MSHC and Ag-MSHC, and we also performed batch adsorption experiments to demonstrate the iodine sorption performance and mechanism by Ag-MSHC. Taking advantage of this combination of MOFs and SOFs, high degree of doping of silver nanoclusters as well as its strong binding ability of iodine, Ag-MSHC can be considered as a superior adsorbent for radioactive iodine extraction. • The Ag-MSHC adsorbents exhibited an extremely high uptake amount of I−. • Ag-MSHC showed a favorable selectivity towards I− in coexisting anions system. • Advanced Ag-MSHC adsorbents can be applied in the nuclear-fuel industry. [ABSTRACT FROM AUTHOR]

• MSONs exhibited an excellent uranium loading capacity (526.6 mg/g) from aqueous solution. • Supramolecular reunion and the collapse of MOFs structure can be effectively avoid. • We proposed a novel melamine-induced strategy to realize a controlled-switching between MOF and SOF. • The as-synthesized MSONs show six different topology architectures during the structural transformation process. SOFs and functionalized-MOFs provide potential opportunities for sequestering uranium from radioactive solution. Nevertheless, the nonporous architecture caused by supramolecular reunion as well as the collapse of MOFs structure by chemical modification step remain an inevitable challenge for further uranium recover and treatment. Herein, we proposed a novel melamine-induced strategy for the first preparation of heterostructured framework (MSONs) based on a self-assembling approach to realize a controlled-switching of structure between MOF and SOF. The MSONs adsorbent was directly constructed using N-donor-containing MA and O-donor-containing TMA as the building units. And then the high-nuclearity metal ions were inserted into the topological structure of SOF to snatch abundant building active sites when they competed with MA to interact with three O-containing linkers on both sides of each TMA molecule. The subsequent chemical modification and supramolecular reunion phenomenon can be effectively avoid by transforming the topology architectures from original MOF-dominated polyhedron to SOF-dominated elongated nanotubes. The obtained MSONs was characterized by SEM, XPS, XRD, TGA and FT-IR spectrometry. Among six kinds of MSONs adsorbents, MSONs-5 exhibited an extremely high UO 2 2+ loading capacity (526.6 mg/g) during the morphological transformation process, which exceeds the most of the previously reported powerful uranium adsorbents. Taking advantage of this extraordinary heterostructured framework and multiple interactions, MA-induced MSONs can be treated as a promising candidate for uranium sequestration. [ABSTRACT FROM AUTHOR]

A novel Ag-doped silicon-based nanosphere (MSA) adsorbent is successfully prepared via a layer-by-layer assembly method for efficient capture of radioactive iodide from aqueous solutions. The Ag 2 O nanoclusters was uniformly embedded into the flexible MPs-SiO 2 to construct a heterogeneous silver platform on the surface of silicon-based materials, resulting in massive generation of high specific binding sites, which were regarded as the strong binding center of radioiodine anion. And incorporation of SiO 2 into the intermediate layer can improve chemical and thermal stability of MSA and protects the core from corrosion of electrochemical reactions. Predominant MSA adsorbent exhibited an excellent adsorption capacity of I− (236.98 mg/g) which was attributed to the irreversible reaction process of AgI solid-liquid interface precipitation between I− and the Ag 2 O nanoclusters of interfacial site-directed growth on MPs-SiO 2. The MSA adsorbent also exhibited a rapid adsorption process and was consistent with the pseudo-second-order kinetics model. Furthermore, the selectivity of the MSA adsorbent for I− was found to be fairly desirable by the adsorption tests under the harsh conditions. These results indicate that superior MSA can find practical applications in the fields of the radionuclides removal and recovery. Unlabelled Image • A novel Ag-doped silicon-based nanospheres were prepared via a layer-by-layer assembly method. • The Ag 2 O nanoclusters uniformly embedded into the flexible MPs-SiO 2. • The Ag 2 O nanoclusters accomplish an interfacial site-directed growth on the surface of silicon-based materials. • Superior MSA exhibited an excellent loading capacities of I− from aqueous solution. [ABSTRACT FROM AUTHOR]