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The potential industrial application of thorium (Th), as well as the environmental and human healthy problems caused by thorium, promotes the development of reliable methods for the separation and removal of Th(IV) from environmental and geological samples. Herein, the phosphonate-amino bifunctionalized mesoporous silica (PAMS) was fabricated by a one-step self-assembly approach for enhancing Th(IV) uptake from aqueous solution. The synthesized sorbent was found to possess ordered mesoporous structures with uniform pore diameter and large surface area, characterized by SEM, XRD, and N2 sorption/desorption measurements. The enhancement of Th(IV) uptake by PAMS was achieved by coupling of an access mechanism to a complexation mechanism, and the sorption can be optimized by adjusting the coverage of the functional groups in the PAMS sorbent. The systemic study on Th(IV) sorption/desorption by using one coverage of PAMS (PAMS12) shows that the Th(IV) sorption by PAMS is fast with equilibrium time of less than 1 h, and the sorption capacity is more than 160 mg/g at a relatively low pH. The sorption isotherm has been successfully modeled by the Langmuir isotherm and D-R isotherm, which reveals a monolayer homogeneous chemisorption of Th(IV) in PAMS. The Th(IV) sorption by PAMS is pH dependent but ionic strength independent. In addition, the sorbed Th(IV) can be completely desorbed using 0.2 mol/L or more concentrated nitric acid solution. The sorption test performed in the solution containing a range of competing metal ions suggests that the PAMS sorbent has a desirable selectivity for Th(IV) ions.

A bifunctional ligand, 2,2'-bipyridine-4,4'-dicarboxylic acid (Hbpdc), has been used in the investigation of constructing bimetallic uranyl organic frameworks (UOFs). Seven novel uranyl-transition metal bimetallic coordination polymers, [(UO)Zn(bpdc)] (1), [Cd(UO)(bpdc)(HO)·2HO] (2), [Cu(UO)(bpdc)(SO)(HO)·2HO] (3), [CuCl(UO)(bpdc)(Hbpdc)(HO)·HO] (4), [Cu(UO)(bpdc)(HO)] (5), [Co(UO)(bpdc)] (6), and [Co(UO)(bpdc)(Hbpdc)(HO)] (7), have been successfully constructed through the assembly of various transition-metal salts, uranyl ions, and Hbpdc ligands under hydrothermal conditions. UOFs 1, 5, 6, and 7 adopt three-dimensional (3D) frameworks with different architectures; UOFs 2 and 3 exhibit two-dimensional (2D) wavelike and stairlike layers, respectively, while UOF 4 is a one-dimensional (1D) chain assembly. These UOFs include a wide range of dimensionalities (1D-3D), interpenetrated frameworks, and cation-cation interaction species, suggesting that anion-dependent structure regulation based on the metalloligand [M(bpdc) ] motifs, the coordination modes of the metal centers and bpdc ligands, along with the reaction temperature, has a remarkable influence on the formation of bimetallic UOFs, which could be a representative system for the structural modulation of UOFs with various dimensionalities and structures. Furthermore, the thermal stability and luminescent properties of compounds 1, 3, and 6 are also investigated.