Herein we present a new viologen‐based radical‐containing metal–organic framework (RMOF) Gd‐IHEP‐7, which upon heating in air undergoes a single‐crystal‐to‐single‐crystal transformation to generate ...Gd‐IHEP‐8. Both RMOFs exhibit excellent air and water stability as a result of favorable radical‐radical interactions, and their long‐lifetime radicals result in wide spectral absorption in the range 200–2500 nm. Gd‐IHEP‐7 and Gd‐IHEP‐8 show excellent activity toward solar‐driven nitrogen fixation, with ammonia production rates of 128 and 220 μmol h−1 g−1, respectively. Experiments and theoretical calculations indicate that both RMOFs have similar nitrogen fixation pathways. The enhanced catalytic efficiency of Gd‐IHEP‐8 versus Gd‐IHEP‐7 is attributed to intermediates stabilized by enhanced hydrogen bonding.
A single‐crystal‐to‐single‐crystal (SCSC) transformation of stable radical‐containing MOF Gd‐IHEP‐7 generates Gd‐IHEP‐8. It is accompanied by a marked increase in efficiency of sacrificial agent‐free photocatalytic nitrogen fixation to yield NH3 from H2O and N2 under simulated solar light irradiation at ambient temperature. The NH3 production rate of 220 μmol h−1 g−1 for Gd‐IHEP‐8 is a new record for MOF photocatalysts.
Elastic metal–organic materials (MOMs) capable of multiple stimuli‐responsiveness based on dual‐stress and thermally responsive triple‐helix coordination polymers are presented. The strong ...metal‐coordination linkage and the flexibility of organic linkers in these MOMs, rather than the 4 Å stacking interactions observed in organic crystals, causes the helical chain to act like a molecular spring and thus accounts for their macroscopic elasticity. The thermosalient effect of elastic MOMs is reported for the first time. Crystal structure analyses at different temperatures reveal that this thermoresponsiveness is achieved by adaptive regulation of the triple‐helix chains by fine‐tuning the opening angle of flexible V‐shaped organic linkers and rotation of its lateral conjugated groups to resist possible expansion, thus demonstrating the vital role of adaptive reorganization of triple‐helix metal–organic chains as a molecular spring‐like motif in crystal jumping.
Dual‐stress and thermally responsive crystalline metal–organic materials (MOMs) based on molecular spring‐like triple‐helix coordination polymers are presented. As the first example of thermosalient effect in elastic MOMs, these compounds undergo elastic flexure upon external stress as well as cracking and jumping after thermal treatment.
•Friction stir processing leads to significant enhancement in corrosion resistance of AZ91alloy.•Corrosion behavior is evaluated by electrochemical, hydrogen evolution and mass loss measurements.•The ...effect of microstructure modification on the corrosion behavior is analyzed.•Beneficial effect of texture and stable β layer on corrosion resistance is documented.
Friction stir processing (FSP) is applied to modify the surface microstructure of cast AZ91 magnesium alloy. The electrochemical and hydrogen evolution measurements reveal that the corrosion rate of processed alloy in 3.5 wt% NaCl solution is significantly decreased. This is mainly attributed to the alteration of corrosion process induced by modification on the morphology and distribution of β-Mg17Al12 phase via FSP. It is originally reported that the formation of a compact and continuous β phase layer on the FSPed surface owing to the segregation of fine β phase effectively enhances the stability and passivity of corrosion product film.
Molecular machines based on mechanically-interlocked molecules (MIMs) such as (pseudo) rotaxanes or catenates are known for their molecular-level dynamics, but promoting macro-mechanical response of ...these molecular machines or related materials is still challenging. Herein, by employing macrocyclic cucurbit8uril (CB8)-based pseudorotaxane with a pair of styrene-derived photoactive guest molecules as linking structs of uranyl node, we describe a metal-organic rotaxane compound, U-CB8-MPyVB, that is capable of delivering controllable macroscopic mechanical responses. Under light irradiation, the ladder-shape structural unit of metal-organic rotaxane chain in U-CB8-MPyVB undergoes a regioselective solid-state 2 + 2 photodimerization, and facilitates a photo-triggered single-crystal-to-single-crystal (SCSC) transformation, which even induces macroscopic photomechanical bending of individual rod-like bulk crystals. The fabrication of rotaxane-based crystalline materials with both photoresponsive microscopic and macroscopic dynamic behaviors in solid state can be promising photoactuator devices, and will have implications in emerging fields such as optomechanical microdevices and smart microrobotics.
Uranyl–organic frameworks (UOFs) have recently been the object of many research endeavors due to the unique coordination mode of uranyl ions and their attractive physicochemical properties. Here, a ...new (3,4)‐connected UOF (U‐IHEP‐4) assembled from uranyl and porphyrin ligand tetrakis(4‐carboxyphenyl)porphyrin (H4TCPP) is reported, which represents the first case of actinide porphyrinic MOFs. Adsorption experiments in DMF solution demonstrated that U‐IHEP‐4 selectively adsorbs positively charged dyes, which is in line with its negatively charged framework and large pore volume ratio (90 %). Remarkably, U‐IHEP‐4 exhibited high catalytic activity for the dehydrogenation of N‐heterocycles to synthesize the corresponding aromatic heterocycles and it can be used as an efficient heterogeneous catalyst.
A new uranyl–organic framework (U‐IHEP‐4) based on porphyrin derivative ligand was synthesized, filling the gap of porphyrinic MOFs in the field of actinide chemistry. The compound U‐IHEP‐4 was demonstrated to be a heterogeneous catalyst for dehydrogenation of N‐heterocycles.
Promoting light absorption range of photocatalysts is of great significance to improve solar light‐driven photocatalytic CO2 reduction efficiency. Herein, a new viologen‐based multicomponent ...heterotrimetallic metal–organic framework (MOF) Cu3Th6(µ3‐O)4(µ3‐OH)4(cpb)12FeIII(CN)66 (IHEP‐14) with an unprecedented (6, 18)‐connected she‐d topology is presented. Upon UV irradiation, this MOF undergoes ligand and iron photoreduction, and a single‐crystal‐to‐single‐crystal transformation to generate persistent radical‐containing MOF Cu3Th6(µ3‐O)4(µ3‐OH)4(cpb•)12FeII(CN)66 (IHEP‐15). This radical‐containing MOF shows excellent stability without fading after at least 2 months in air. Besides extending the photoabsorption to a wider wavelength range covering from 200 to 2,500 nm, the generation of persistent radical in IHEP‐15 also largely enhances its CO2 adsorption capacity by a factor of three due to the strong affinity between π orbital of the radical and the π system of CO2. These attributes endow IHEP‐15 with excellent visible/NIR light‐driven CO2 photoreduction activity, with CO production rates under visible and NIR irradiation of 570.3 and 209.3 µmol h−1 g−1, respectively. Notably, the latter is a record high for NIR‐induced CO production among all MOFs reported so far.
A single‐crystal‐to‐single‐crystal (SCSC) transformation of unprecedented (6, 18)‐connected multicomponent MOF IHEP‐14 generates persistent radical‐containing MOF IHEP‐15, accompanied by a marked increase in CO2 sorption and visible/NIR photocatalytic reduction of CO2 to CO with high selectivity. The NIR light‐driven CO production rate of 209.3 µmol h−1 g−1 for IHEP‐15 is recorded high for NIR‐induced CO production among all MOFs reported so far.
We demonstrate the recently proposed nucleon energy-energy correlator (NEEC) f_{EEC}(x,θ) can unveil the gluon saturation in the small-x regime in eA collisions. The novelty of this probe is that it ...is fully inclusive just like the deep-inelastic scattering (DIS), with no requirements of jets or hadrons but still provides an evident portal to the small-x dynamics through the shape of the θ distribution. We find that the saturation prediction is significantly different from the expectation of the collinear factorization.
A preorganized tetradentate phenanthrolineamide (DAPhen) ligand with hard and soft donors combined in the same molecule has been found to possess high extraction ability toward actinides over ...lanthanides from acidic aqueous solution in our previous work. Herein we grafted phenanthrolineamide groups onto a large-pore three-dimensional cubic silica support by the reaction of DAPhen siloxane with KIT-6 substrate to prepare a novel uranium-selective sorbent, KIT-6-DAPhen. The as-synthesized sorbent was well-characterized by scanning electron microscopy, high-resolution transmission electron microscopy, N2 adsorption/desorption, X-ray diffraction, FT-IR, 13C cross-polarization magic-angle spinning NMR, and TGA techniques, which confirmed the consummation of the functionalization. Subsequently, the effects of contact time, solution pH, initial U(VI) concentration, and the presence of competing metal ions on the U(VI) sorption onto KIT-6-DAPhen sorbent were investigated in detail. It was found that KIT-6-DAPhen showed largely enhanced sorption capacity and excellent selectivity toward U(VI). The maximum sorption capacity of KIT-6-DAPhen at pH 5.0 reaches 328 mg of U/g of sorbent, which is superior to most of functionalized mesoporous silica materials. Density functional theory coupled with quasi-relativistic small-core pseudopotentials was used to explore the sorption interaction between U(VI) and KIT-6-DAPhen, which gives a sorption reaction of KIT-6-DAPhen + UO2(H2O)52+ + NO3 – ⇄ UO2(KIT-6-DAPhen)(NO3)+ + 5H2O. The findings of the present work provide new clues for developing new actinide sorbents by combining new ligands with various mesoporous matrixes.
c-Myc is known to promote glutamine usage by upregulating glutaminase (GLS), which converts glutamine to glutamate that is catabolized in the TCA cycle. Here we report that in a number of human and ...murine cells and cancers, Myc induces elevated expression of glutamate-ammonia ligase (GLUL), also termed glutamine synthetase (GS), which catalyzes the de novo synthesis of glutamine from glutamate and ammonia. This is through upregulation of a Myc transcriptional target thymine DNA glycosylase (TDG), which promotes active demethylation of the GS promoter and its increased expression. Elevated expression of GS promotes cell survival under glutamine limitation, while silencing of GS decreases cell proliferation and xenograft tumor growth. Upon GS overexpression, increased glutamine enhances nucleotide synthesis and amino acid transport. These results demonstrate an unexpected role of Myc in inducing glutamine synthesis and suggest a molecular connection between DNA demethylation and glutamine metabolism in Myc-driven cancers.
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•Myc induces expression of glutamine synthetase (GS)•Increased GS expression is mediated by TDG-mediated promoter demethylation•GS promotes biosynthesis of asparagine and ribonucleotides, and amino acid transport•Suppression of GS decreases cell survival, proliferation, and oncogenesis
Bott et al. reveal that oncogenic Myc induces active DNA demethylation to increase glutamine synthetase (GS) expression and boost glutamine-dependent anabolic processes, including nucleotide synthesis and amino acid transport. GS modulates cell sensitivity to glutamine shortage, as well as proliferation and tumorigenesis.
As a less explored avenue, actinide‐based metal‐organic frameworks (MOFs) are worth studying for the particularity of actinide nodes in coordination behaviour and assembly modes. In this work, an ...azobenzenetetracarboxylate‐based anionic MOF supported by uranyl–carboxyl helical chain units was synthesized, incorporating linear uranyl as the metal centre. This kind of helical chain‐type building unit is reported for the first time in uranyl‐based MOFs. Structural analysis reveals that the formation of helical chain secondary units can be attributed to restricted equatorial coordination of rigid flat azobenzene ligand to uranyl centres. Meanwhile, this newly‐synthesized anionic material has been used to remove Eu3+ ions, as a non‐radioactive surrogate of Am3+ ion, through an ion‐exchange process with (CH3)2NH2+ ions in its open channels, as evidenced by a combination of 1H NMR spectroscopy, EDS and PXRD.
Chain gang: An anionic uranyl–organic framework supported by metal‐carboxyl helical chain units can selectively remove Eu3+ ion, a non‐radioactive surrogate of Am3+ ion, through ion‐exchange with (CH3)2NH2+ ions in its open channels.
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