Regenerable and Highly Stable Two-Dimensional Imine-Based Covalent Organic Framework for Simultaneous Rapid Detection and Adsorption of Cu2+ Ions.

The development of efficient fluorescent probes and adsorbents for detecting and removing Cu2+, which pose potential environmental and health risks, is a highly active area of research. However, achieving simultaneously improved fluorescence detection efficiency and enhanced adsorption capacity in a single porous probe remains a significant challenge. In this study, we successfully synthesized a two-dimensional imine-based TAP-COF using 2,4,6-triformylphloroglucinol and tri(4-aminophenyl)amine as raw materials. TAP-COF exhibited excellent properties, including a large specific surface area of 685.65 m2·g-1, exceptional thermal stability (>440 °C), chemical stability, temporal stability, and recyclability. Fluorescence testing revealed that TAP-COF exhibited remarkable specificity and high sensitivity for detecting Cu2+. The fluorescence mechanism, in which the excited state intramolecular proton transfer was impeded by the interaction of Cu2+ with C═O and C-N bonds on TAP-COF upon the addition of Cu2+, was further elucidated through experimental and theoretical methods. Furthermore, the adsorption capacity of TAP-COF toward Cu2+ was investigated, confirming the excellence of TAP-COF as a fluorescent probe and adsorbent for the specific detection and removal of Cu2+. This work holds significant implications for improving environmental and human health concerns associated with Cu2+ contamination.

New Insight into U@C80: Missing U@D3(31921)-C80 and Nuanced Enantiomers of U@C1(28324)-C80.

Triplet U@C1(28324)-C80, violating the isolated pentagon rule, is experimentally recognized as the stable isomer for uranium-based endohedral monometallofullerene U@C80. Here we first verified that triplet U@D3(31921)-C80, following the isolated pentagon rule, was to be another thermodynamically stable isomer via density functional theory in conjunction with statistical thermodynamic analysis. U@D3(31921)-C80 was probably missing in the previous experiment and would be a promising isomer in the to-be experiment because of its excellently thermodynamic stability. In addition, the anomalous metal position was revealed in U@D3(31921)-C80 and U@C1(28324)-C80. Four-electron transfer from U to C80 was also revealed for the two isomers. Thus, two unpaired 5f electrons were still in the U for U@D3(31921)-C80 and U@C1(28324)-C80. Moreover, the covalent interactions between U and C80 in U@D3(31921)-C80 were stronger than those in U@C1(28324)-C80. The electrostatic interactions preponderated in the interaction energy ΔEint between U and C80 for U@C1(28324)-C80, and the orbital interactions dominated in the ΔEint for U@D3(31921)-C80. The electrophilic and nucleophilic reactivities were also analyzed for U@D3(31921)-C80 and U@C1(28324)-C80. Electronic circular dichroism spectra were simulated to distinguish the two enantiomers of U@C1(28324)-C80. We are hopeful that this investigation will be valuable for further identification of the two enantiomers in future experiments.

Pivotal Role of Nonmetal Atoms in the Stabilities, Geometries, Electronic Structures, and Isoelectronic Chemistry of Sc3 X@C80 (X = C, N, and O).

The thermodynamic and dynamic stabilities of Sc3 X@C80 (X = C, N, and O) are explored via density functional theory combined with statistical thermodynamic analysis and ab initio molecular dynamics. It is the first time to comprehensively consider the effect of nonmetal atoms on trimetallic endohedral clusterfullerenes. Relative to Sc3 X@Ih (31924)-C80 (X = N and O) with general six-electron transfer, an intriguing electronic structure of unexplored Sc3 C@D5h (31923)-C80 with thermodynamic and dynamic stabilities is clearly disclosed. Natural bond orbitals and charge decomposition analysis simultaneously suggest that one unpaired electron appears on the cage for neutral Sc3 C@D5h (31923)-C80 , which could be prospectively stabilized by effective exohedral derivatization and ionization in the future. Moreover, isoelectronic endohedral clusterfullerenes, (Sc3 C@C80 )- , Sc3 N@C80 , and (Sc3 O@C80 )+ , are also uniquely taken into account. The geometries, electronic structures, reactivities, and reactive sites of isoelectronic species are examined, and it turns out that all the three isoelectronic species would rather electrophilic than nucleophilic reactions. © 2019 Wiley Periodicals, Inc.

In-Depth Theoretical Probe into Novel Mixed-Metal Uranium-Based Endohedral Clusterfullerenes Sc2UX@Ih(31924)-C80 (X = C, N).

Mixed-metal uranium-based endohedral clusterfullerenes, Sc2UX@C80 (X = C, N), which were recently reported in experiments, have been investigated considering heptagon-containing isomers by density functional theory calculations in conjunction with statistical thermodynamic analysis. The triplet Sc2UC@Ih(31924)-C80 and quartet Sc2UN@Ih(31924)-C80, named after the spiral number (31924), are found to be thermodynamically stable and satisfy aromaticity rules. Furthermore, the restricted movements of the Sc2UX (X = C, N) cluster in Ih(31924)-C80 have been demonstrated via ab initio molecular dynamics simulations. The six-electron transfer from the inner cluster to the cage results in the electronic structures (Sc2UX)6+@C806- (X = C, N), which were also confirmed by natural bond orbital analysis. On the basis of the frontier molecular orbitals, the oxidation states of uranium in Sc2UC@C80 and Sc2UN@C80 are +IV and +III, respectively, with residual electrons in 5f orbitals of U. The chemical bond between U and C (N) of the inner cluster is characterized as a double bond (single bond) by an analysis of the Mayer bond orders. There are covalent interactions between the inner cluster and outer cage, which is clarified by the quantum theory of atoms in molecules. IR spectra of the optimal isomers have also been simulated, which show the clear difference between Sc2UX@C80 (X = C, N). These findings, together with simulated results, are expected to supply useful information in future experiments of mixed-metal uranium-based endohedral clusterfullerenes.