Metal−organic frameworks (MOFs)highly crystalline hybrid materials that combine metal ions with rigid organic ligandshave emerged as an important class of porous materials. The organic ligands add ...flexibility and diversity to the chemical structures and functions of these materials. In this Account, we summarize our laboratory’s experience in tuning the topology and functionality of MOFs by ligand design. These investigations have led to new materials with interesting properties. By using a ligand that can adopt different symmetry conformations through free internal bond rotation, we have obtained two MOFs that are supramolecular stereoisomers of each other at different reaction temperatures. In another case, where the dimerized ligands function as a D 3-Piedfort unit spacer, we achieve chiral (10,3)-a networks. In the design of MOF-based materials for hydrogen and methane storage, we focused on increasing the gas affinity of frameworks by using ligands with different geometries to control the pore size and effectively introduce unsaturated metal centers (UMCs) into the framework. Framework interpenetration in PCN-6 (PCN stands for porous coordination network) can lead to higher hydrogen uptake. Because of the proper alignment of the UMCs, PCN-12 holds the record for uptake of hydrogen at 77 K/760 Torr. In the case of methane storage, PCN-14 with anthracene-derived ligand achieves breakthrough storage capacity, at a level 28% higher than the U.S. Department of Energy target. Selective gas adsorption requires a pore size comparable to that of the target gas molecules; therefore, we use bulky ligands and network interpenetration to reduce the pore size. In addition, with the help of an amphiphilic ligand, we were able to use temperature to continuously change pore size in a 2D layer MOF. Adding charge to an organic ligand can also stabilize frameworks. By ionizing the amine group within mesoMOF-1, the resulting electronic repulsion keeps the network from collapsing, giving rise to the first case of mesoporous MOF that demonstrates the type IV isotherm. We use dendritic hexacarboxylate ligands to synthesize an isoreticular series of MOFs with (3,24)-connected network topology. The cuboctahedral cages serve as building blocks that narrow the opening of the mesocavities into microwindows and stabilize these MOFs. The resulting materials have exceptionally high surface areas and hydrogen uptake capacities. Despite the many achievements in MOF development, there is still ample opportunity for further exploration. We will be continuing our efforts and look forward to contributing to this blossoming field in the next decade.
Chimonobambusa pleiacantha
, a newly-identified species of the genus
Chimonobambusa
Makino from southeast Sichuan, China, is meticulously described and illustrated herein. It is morphologically ...similar to
Ch. tuberculata
, but differs in having 4-angled internodes, thicker wall to 4.5–8.5 mm, more reclinate and elongated root thorns to 5–8 mm long, culm internodes with three grooves and two longitudinal ridges on the branch-bearing side, persistent culm leaves, densely brown-purple setose at the bottom of culm leaf sheaths together with sheath scar, developed foliage leaf fimbriae, 6–8 on each shoulder, ca. 3–8 mm long, abaxially white pubescent foliage leaf blades. Phenologically, new shoots usually appear in September to October. In the light of these key morphological and phenological characteristics,
Ch. pleiacantha
was identified as a new species of the genus
Ch.
Makino which is different from published species of this genus.
Surmounting the inhomogeniety issue of gas sensors and realizing their reproducible ppb‐level gas sensing are highly desirable for widespread deployments of sensors to build networks in applications ...of industrial safety and indoor/outdoor air quality monitoring. Herein, a strategy is proposed to substantially improve the surface homogeneity of sensing materials and gas sensing performance via chip‐level pyrolysis of as‐grown ZIF‐L (ZIF stands for zeolitic imidazolate framework) films to porous and hierarchical zinc oxide (ZnO) nanosheets. A novel approach to generate adjustable oxygen vacancies is demonstrated, through which the electronic structure of sensing materials can be fine‐tuned. Their presence is thoroughly verified by various techniques. The sensing results demonstrate that the resultant oxygen vacancy‐abundant ZnO nanosheets exhibit significantly enhanced sensitivity and shortened response time toward ppb‐level carbon monoxide (CO) and volatile organic compounds encompassing 1,3‐butadiene, toluene, and tetrachloroethylene, which can be ascribed to several reasons including unpaired electrons, consequent bandgap narrowing, increased specific surface area, and hierarchical micro–mesoporous structures. This facile approach sheds light on the rational design of sensing materials via defect engineering, and can facilitate the mass production, commercialization, and large‐scale deployments of sensors with controllable morphology and superior sensing performance targeted for ultratrace gas detection.
A facile approach for designing sensing materials via rational defect engineering to tune the electronic structure of on‐chip MOF‐derived hierarchical ZnOs and thus sensing properties is proposed. The resultant homogeneous ZnO layer with abundant oxygen vacancies exhibits significantly enhanced sensitivity and short response time toward ppb‐level carbon monoxide and volatile organic compounds.
Rechargeable Zn-air batteries are under intensive studies because of their high-energy density, low cost, and safety. However, their wide application is prevented by several remaining technical ...issues, one of which is the lack of suitable bifunctional cathodic catalysts for oxygen reduction reaction (ORR) during discharging and oxygen evolution reaction (OER) during charging. Due to low material cost and wide distribution, carbon-based materials may serve as promising electrocatalysts, while doping heteroatoms such as nitrogen or boron can effectively enhance their catalytic activity. Herein, we pyrolyze a metal-organic framework containing Zn, N, and B as the precursor to synthesize dual-doped and metal-free porous carbon materials as efficient ORR/OER bifunctional electrocatalysts. The surface area of obtained carbon materials can be greatly enhanced by pyrolysis under H2-containing atmosphere. In addition, N and B are evenly distributed within the carbon materials due to the crystalline MOF precursor. The resultant carbon materials exhibit high ORR and OER catalytic activities in both half-cell and single-cell battery measurements. Our study has demonstrated for the first time that MOFs can be used as precursors to synthesize metal-free ORR/OER bifunctional cathodic electrocatalysts with great potential in rechargeable Zn-air batteries.
New geochronological and geochemical data on magmatic activity from the India-Asia collision zone enables recognition of a distinct magmatic flare-up event that we ascribe to slab breakoff. This ...tie-point in the collisional record can be used to back-date to the time of initial impingement of the Indian continent with the Asian margin. Continental arc magmatism in southern Tibet during 80-40 Ma migrated from south to north and then back to south with significant mantle input at 70-43 Ma. A pronounced flare up in magmatic intensity (including ignimbrite and mafic rock) at ca. 52-51 Ma corresponds to a sudden decrease in the India-Asia convergence rate. Geological and geochemical data are consistent with mantle input controlled by slab rollback from ca. 70 Ma and slab breakoff at ca. 53 Ma. We propose that the slowdown of the Indian plate at ca. 51 Ma is largely the consequence of slab breakoff of the subducting Neo-Tethyan oceanic lithosphere, rather than the onset of the India-Asia collision as traditionally interpreted, implying that the initial India-Asia collision commenced earlier, likely at ca. 55 Ma.
Catalytic transfer hydrogenation is an attractive route for the synthesis of biomass-derived chemicals. However, development of efficient, low-cost, and stable catalysts for that reaction is still a ...challenge. Here, we report on the preparation and testing of a non-noble perovskite oxide (LaFeO3) catalyst synthesized by an in situ carbon templating method. We show that our catalyst is quite active and selective toward the hydrogenation of unsaturated organics. Compared to an analogous LaFeO3 catalyst prepared by a more traditional method, using citric acid, the new LaFeO3 exhibited a more porous structure, a La-enriched surface composition, and abundant oxygen vacancies, all characteristics that improve contact with the reactants. In the case of the conversion of furfural to furfuryl alcohol (FOL) using iso-propanol as hydrogen donor, the new LaFeO3 showed a furfural conversion of 90% and a selectivity to FOL of 94%, significantly higher than with the reference LaFeO3 prepared by the traditional sol–gel method (60 and 91%, respectively). Moreover, our new LaFeO3 catalyst can be recovered after a calcination treatment, with no appreciable changes in its structure or activity, a test that we repeated six times, and can promote the hydrogenation of other carbonyl compounds containing electron-withdrawing groups. A reaction mechanism is proposed in which metal cations are the adsorption sites for iso-propanol and oxygen vacancies are the adsorption sites for furfural, and where the conversion proceeds following an acid–base mechanism. We believe that the novel use of perovskites as catalysts for hydrogenation reactions reported here may be easily extendable to other processes, and that our carbon-templating synthetic approach offers a way to synthesize viable perovskite catalysts with high surface areas for optimized activity.
Inspired by the special reducing capability of ascorbic acid (AA), ascorbic acid 2-phosphate (AA2P) has been extensively utilized as a substrate in current alkaline phosphatase (ALP) activity assays ...owing to the ALP-triggered transformation of AA2P into AA. However, such assays usually require AA-related complicated and laborious synthesis and/or signal generation procedures. Herein, we report an interesting in situ fluorogenic interaction between o-phenylenediamine (OPD) and AA, which inspires us to put forward a novel and simple AA2P/OPD-participated fluorescence turn-on ALP activity assay for the first time, and then the corresponding ALP-based fluorescence enzyme-linked immunosorbent assay (ELISA) has also been developed by means of the conventional ELISA platforms. According to the convenient and facile detection process with clear response mechanism, our fluorogenic reaction-based assay exhibits good sensitivity, selectivity, and excellent sensing performance, which ensures fluorescence ELISA to potentially be applied in clinical diagnosis by employing a well-studied biomarker of hepatocellular carcinoma, α-fetoprotein (AFP) as the model analyte. Such original ELISA via in situ formation of fluorophore from scratch gives a new sight to develop other potential immunoassay platforms in early clinical diagnosis by controlling the target antigens in the near future.
Isoreticular functionalization is a well‐elucidated strategy for pore environment tuning and the basis of gas separation performance in extended frameworks. The extension of this approach to discrete ...porous molecules such as metal‐organic cages (MOCs) is conceptually straightforward but hindered by synthetic complications, especially stability concerns. We report the successful isoreticular functionalization of a zirconium MOC with tetrazole moiety by bottom‐up synthesis. The title compound (ZrT‐1‐tetrazol) shows promising C2H2/CO2 and C2H2/C2H4 separation performance, as demonstrated by adsorption isotherms, breakthrough experiments, and density functional theory calculations. The design analogy between MOFs and highly stable MOCs may guide the synthesis of novel porous materials for challenging separation applications.
We report the use of isoreticular chemistry to synthesize a tetrazole‐functionalized metal‐organic cage (ZrT‐1‐tetrazol) with the same structure of ZrT‐1 and ZrT‐1‐NH2. The adsorption capacity of ZrT‐1‐tetrazol for C2H2 increases by 130 % (298 K) compared with ZrT‐1‐NH2, and it exhibits promising C2H2/CO2 and C2H2/C2H4 separation performance.
Background and Purpose
Non‐alcoholic steatohepatitis (NASH) is the more severe form of metabolic associated fatty liver disease (MAFLD) and no pharmacological treatment as yet been approved. ...Identification of novel therapeutic targets and their agents is critical to overcome the current inadequacy of drug treatment for NASH.
Experimental Approach
The correlation between heat shock factor 1 (HSF1) levels and the development of NASH and the target genes of HSF1 in hepatocyte were investigated by chromatin‐immunoprecipitation sequencing. The effects and mechanisms of SYSU‐3d in alleviating NASH were examined in relevant cell models and mouse models (the Ob/Ob mice, high‐fat and high‐cholesterol diet and the methionine‐choline deficient diet‐fed mice). The actions of SYSU‐3d in vivo were evaluated.
Key Results
HSF1 is progressively reduced with mitochondrial dysfunction in NASH pathogenesis and activation of this transcription factor by its newly identified activator SYSU‐3d effectively inhibited all manifestations of NASH in mice. When activated, the phosphorylated HSF1 (Ser326) translocated to nucleus and bound to the promoter of PPARγ coactivator‐1α (PGC‐1α) to induce mitochondrial biogenesis. Thus, increasing mitochondrial adaptive oxidation and inhibiting oxidative stress. The deletion of HSF1 and PGC‐1α or recovery of HSF1 in HSF1‐deficiency cells showed the HSF1/PGC‐1α pathway was mainly responsible for the anti‐NASH effects of SYSU‐3d independent of AMP‐activated protein kinase (AMPK).
Conclusion and Implications
Activation of HSF1 is a practical therapeutic approach for NASH treatment via the HSF1/PGC‐1α/mitochondrial pathway and SYSU‐3d can be considered as a potential candidate for the treatment of NASH.
The molecular mode of SYSU‐3d action against NASH is dependent on the HSF1/PGC‐1α/mitochondrial pathway, which initially increases lipid oxidation followed by decreases oxidative stress, preventing injury, inflammation, and fibrosis. Our combined findings indicate that correction of the HSF1 suppression can be utilised as a practicable therapeutic approach for the treatment of NASH.
Isolation of CO2 from acetylene (C2H2) via CO2‐selective sorbents is an energy‐efficient technology for C2H2 purification, but a strategic challenge due to their similar physicochemical properties. ...There is still no specific methodology for constructing sorbents that preferentially trap CO2 over C2H2. We report an effective strategy to construct optimal pore chemistry in a CeIV‐based ultramicroporous metal–organic framework CeIV‐MIL‐140‐4F, based on charge‐transfer effects, for efficient inverse CO2/C2H2 separation. The ligand‐to‐metal cluster charge transfer is facilitated by CeIV with low‐lying unoccupied 4f orbitals and electron‐withdrawing F atoms functionalized tetrafluoroterephthalate, affording a perfect pore environment to match CO2. The exceptional CO2 uptake (151.7 cm3 cm−3) along with remarkable separation selectivities (above 40) set a new benchmark for inverse CO2/C2H2 separation, which is verified via simulated and experimental breakthrough experiments. The unique CO2 recognition mechanism is further unveiled by in situ powder X‐ray diffraction experiments, Fourier‐transform infrared spectroscopy measurements, and molecular calculations.
A charge‐ or electron‐transfer strategy within confined pore space is reported for the design of CO2‐selective ultramicroporous metal–organic frameworks with specific pore environments. Using this strategy, high CO2 capacities and high‐purity C2H2 (> 99.9%) were obtained as proven by fixed bed breakthrough experiments.
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