In this study, a carboxyl-functionalized covalent organic framework (COF) rich in nitrogen (N) and oxygen (O) functional groups was prepared and characterized, which provided a new opportunity for the efficient and rapid treatment of radioactive contamination in nuclear wastewater. The synthesis of the COF (Tp-DTA) was constructed using 1,3,5-triformylphloroglucinol (TFP) and 2,5-diaminoterephthalic acid (DTA), providing a large specific surface area, mesoporous pore, and abundant coordination sites with high adsorption capacity and exceptional affinity for Sr 2+ . Batch adsorption experiments exhibited that Tp-DTA achieved a maximum adsorption capacity of 145.4 mg/g for Sr 2+ in alkaline solutions, reaching adsorption equilibrium within 60 min. Tp-DTA exhibited rapid kinetics for 90 Sr, with the amounts of 90 Sr removed more than 95% within 3 min. In the presence of coexisting ions (Na + , K + , Cs + , Mg 2+ , and Ca 2+ ), Tp-DTA displayed excellent preferential selectivity for Sr 2+ and high removal efficiency. Even in simulated groundwater containing multiple complex ions, Tp-DTA demonstrated a strong affinity for Sr 2+ and showed practical applicability with a nearly 100% removal efficiency for 90 Sr. XPS and FTIR characterizations confirmed that the adsorption mechanism of Sr 2+ involved chelation exchange between the carboxyl groups of Tp-DTA and Sr 2+ in the solution. Furthermore, the desorption efficiency of HCl (>0.01 mol/L) can reach 95% and five cyclic desorption-adsorption experiments demonstrated the reusability of Tp-DTA, endowing the carboxyl-functional COF with great potential in the treatment of 90 Sr-contaminated radioactive wastewater and environmental remediation.
Kai-Yao Wang,Yang Liu,Jia-Ying Zhu,Lin Cheng,Cheng Wang
Deep investigations on the synthetic and structural chemistry of heterometallic chalcogenidostannates bear fundamental significance for the establishment of the structure–property relationship that would offer guidance on the functional material innovation. Presented here are four ammonium- and/or alkylammonium-directed M–Sn–Q (M = Zn, Cd; Q = S, Se) compounds, namely, [NH4]7[H3O]3Zn4Sn4S17 (1), [NH4]5[(CH3)2NH2]Zn4Sn5S17 (2), [CH3CH2NH3]22Zn16Sn12Se51(H2O)4·16H2O (3), and [NH4]2CdSnSe4 (4). All four compounds were synthesized in deep eutectic solvents (DESs) or ethylamine aqueous solution, both of which function simultaneously as reaction media and structure-directing agents. Compound 1 consists of discrete P1-[Zn4Sn4S17]10– clusters templated by mixed [NH4]+/[H3O]+ cations. In compound 2, such P1 clusters are bridged by Sn4+ ions in a 4,4-connection mode to form a [Zn4Sn5S17]n6n– framework with three types of cavities (I–III) varying in size. The two smaller cavities (I and II) accommodate NH4+ while the larger one(III) is occupied by [(CH3)2NH2]+, reflecting the rational size-dependence of cations on cavities. Compound 3 features an [Zn16Sn12Se51(H2O)4]n22n– open framework constructed from the 4,3-connection of P1-[Zn4Sn4Se17]10– clusters and {Zn(H2O)}2+ bridges. This linkage mode contributes to a large cage-like subunit (inner dimension: 21.99 × 9.06 Å2) and therefore an ultrahigh porosity that are occupied by [CH3CH2NH3]+ cations and water molecules (volume fraction: 57.7%). Compound 4 exists as a stacking of [CdSnSe4]n2n– chains, which are composed of alternatively arranged {CdSe4} and {SnSe4} tetrahedra, in combination with [NH4]+ cations as both charge-compensating and space-filling agents. Detailed synthetic, structural, and topological analyses were performed on these solid materials, coupled with extensive investigations on their optical and thermal properties. Compound 3 exhibits an efficient Sr2+ adsorption performance, featuring ultrafast kinetics (94.69% in 5 min), high removal rate (98.57% in 20 min) at equilibrium, and high capacity (104.17 ± 23.53 mg g–1).
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