The controlled synthesis of multicomponent metal–organic frameworks (MOFs) allows for the precise placement of multiple cooperative functional groups within a framework, leading to emergent ...synergistic effects. Herein, we demonstrate that turn‐on fluorescence sensors can be assembled by combining a fluorophore and a recognition moiety within a complex cavity of a multicomponent MOF. An anthracene‐based fluorescent linker and a hemicyanine‐containing CN−‐responsive linker were sequentially installed into the lattice of PCN‐700. The selective binding of CN− to hemicyanine inhibited the energy transfer between the two moieties, resulting in a fluorescence turn‐on effect. Taking advantage of the high tunability of the MOF platform, the ratio between anthracene and the hemicyanine moiety could be fine‐tuned in order to maximize the sensitivity of the overall framework. The optimized MOF‐sensor had a CN−‐detection limit of 0.05 μm, which is much lower than traditional CN− fluorescent sensors (about 0.2 μm).
An anthracene‐based fluorescent linker and a hemicyanine‐containing CN−‐responsive linker were sequentially installed into the lattice of the metal–organic framework PCN‐700. The proximity and periodic arrangement of the anthracene and hemicyanine linkers facilitated efficient energy transfer between the two components, causing fluorescence quenching. The binding of CN− to hemicyanine inhibited this energy transfer, resulting in fluorescence.
Multi‐component metal–organic frameworks (MOFs) with precisely controlled pore environments are highly desired owing to their potential applications in gas adsorption, separation, cooperative ...catalysis, and biomimetics. A series of multi‐component MOFs, namely PCN‐900(RE), were constructed from a combination of tetratopic porphyrinic linkers, linear linkers, and rare‐earth hexanuclear clusters (RE6) under the guidance of thermodynamics. These MOFs exhibit high surface areas (up to 2523 cm2 g−1) and unlimited tunability by modification of metal nodes and/or linker components. Post‐synthetic exchange of linear linkers and metalation of two organic linkers were realized, allowing the incorporation of a wide range of functional moieties. Two different metal sites were sequentially placed on the linear linker and the tetratopic porphyrinic linker, respectively, giving rise to an ideal platform for heterogeneous catalysis.
A series of multi‐component MOFs, namely PCN‐900(RE), were constructed from a combination of tetratopic porphyrinic linkers, linear linkers, and rare‐earth hexanuclear clusters (RE6) under the guidance of thermodynamics. Pore‐environment engineering with precisely placed metal sites was realized in these MOFs, which led to the formation of an efficient heterogeneous catalytic system.
Crystal engineering of metal-organic frameworks (MOFs) has allowed the construction of complex structures at atomic precision, but has yet to reach the same level of sophistication as organic ...synthesis. The synthesis of complex MOFs with multiple organic and/or inorganic components is ultimately limited by the lack of control over framework assembly in one-pot reactions. Herein, we demonstrate that multi-component MOFs with unprecedented complexity can be constructed in a predictable and stepwise manner under simple kinetic guidance, which conceptually mimics the retrosynthetic approach utilized to construct complicated organic molecules. Four multi-component MOFs were synthesized by the subsequent incorporation of organic linkers and inorganic clusters into the cavity of a mesoporous MOF, each composed of up to three different metals and two different linkers. Furthermore, we demonstrated the utility of such a retrosynthetic design through the construction of a cooperative bimetallic catalytic system with two collaborative metal sites for three-component Strecker reactions.
A major goal of metal-organic framework (MOF) research is the expansion of pore size and volume. Although many approaches have been attempted to increase the pore size of MOF materials, it is still a ...challenge to construct MOFs with precisely customized pore apertures for specific applications. Herein, we present a new method, namely linker labilization, to increase the MOF porosity and pore size, giving rise to hierarchical-pore architectures. Microporous MOFs with robust metal nodes and pro-labile linkers were initially synthesized. The mesopores were subsequently created as crystal defects through the splitting of a pro-labile-linker and the removal of the linker fragments by acid treatment. We demonstrate that linker labilization method can create controllable hierarchical porous structures in stable MOFs, which facilitates the diffusion and adsorption process of guest molecules to improve the performances of MOFs in adsorption and catalysis.
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•A recovery system with LiMn2O4/Li1-xMn2O4 as electrodes was used to extract lithium.•The influence sequence of coexisting ions on lithium extraction was Mg2+> Na+> Ca2+> K+.•The ...values of αLi-Na, αLi-Mg and αLi-Ca were more than 300, 70 and 110, respectively.•The specific energy consumption was between 18 and 19W h·mol−1.
Lithium rechargeable batteries have been used for lithium extraction in recent years. Here, we report on a highly selective lithium recovery system that consists of a LiMn2O4 positive electrode, a Li1-xMn2O4 negative electrode and a monovalent selective anion-exchange membrane. The effect of potential, temperature and coexisting ions on lithium extraction were investigated in this paper, and the lithium recovery system was applied to extract lithium from brine and concentrated seawater. The extraction capacity of Li+ reached 34.31 mg· (1g LiMn2O4) −1 at 1.2V. With higher reaction rate and lower energy consumption, 25°C (room temperature) was considered as the appropriate temperature. The system still remained high selective for Li+ even in the presence of impurity ions (K+, Na+, Mg2+, Ca2+). With simulated brine and concentrated seawater as source solutions, the concentrations of Na+, Mg2+ and Ca2+ were reduced more than 300, 70 and 100 times, consuming 18–19W h per mole of lithium recovered. And the electrodes still had high separation coefficients of Li+ and Men+ (Na+, Mg2+, Ca2+) after five cycles although a slight drop was existing.
Heterometallic metal–organic frameworks (MOFs) allow the precise placement of various metals at atomic precision within a porous framework. This new level of control by MOFs promises fascinating ...advances in basic science and application. However, the rational design and synthesis of heterometallic MOFs remains a challenge due to the complexity of the heterometallic systems. Herein, we show that bimetallic MOFs with MX2(INA)4 moieties (INA=isonicotinate; M=Co2+ or Fe2+; X=OH−, Cl−, Br−, I−, NCS−, or NCSe−) can be generated by the sequential modification of a Zr‐based MOF. This multi‐step modification not only replaced the linear organic linker with a square planar MX2(INA)4 unit, but also altered the symmetry, unit cell, and topology of the parent structure. Single‐crystal to single‐crystal transformation is realized so that snapshots for transition process were captured by successive single‐crystal X‐ray diffraction. Furthermore, the installation of Co(NCS)2(INA)4 endows field‐induced slow magnetic relaxation property to the diamagnetic Zr‐MOF.
MOF metamorphosis: A series of heterometallic metal–organic frameworks (MOFs) was synthesized by sequential modification of a Zr‐based MOF. The multi‐step modification alters the symmetry, topology, and unit cell of the framework while maintaining its single crystallinity. Furthermore, the postsynthetically introduced Co(NCS)2(pyridine)4 moiety endows field‐induced slow magnetic relaxation to the diamagnetic Zr‐MOF.
The process for separating and purifying lithium in brines based on electrodialysis with monovalent selective ion exchange membranes was investigated in our previous work. The migration of coexisting ...cations in brines was competitive with lithium ions, especially monovalent cations (Na+ and K+). The aim of this study was to examine the influence of major coexisting cations in brines on lithium recovery in the selective-electrodialysis (S-ED) process. Considering the factors of coexisting cations, such as concentration and type, some migration laws of lithium ion were found as follows: the concentration of coexisting cations had negative effect on the migration of lithium ion; the influence order of coexisting cations on lithium migration was contrary to their hydrated radius sequence: K+>Na+>Ca2+>Mg2+. In order to characterize the migration process of cations through monovalent selective cation exchange membrane in microcosmic theory, a partial dehydration conceptual model based on charge capillary column theory and ionic potential was proposed. And the model was used to characterize the ions migration process. Simultaneously, considering the hydration potential which indicates how strongly an ion would attract water molecules, the influence sequence of coexisting cations was explained legitimately. These observations might provide some theoretical basis and technological support for the relevant research of recovering lithium from brines.
A partial dehydration conceptual model of ion migration in the cation exchange membrane. Display omitted
•Selective-electrodialysis (S-ED) was used to recover lithium from brine.•Effect of coexisting cations concentration on lithium recovery by S-ED was investigated.•The influence sequence of coexisting cations on lithium migration was K+>Na+>Ca2+>Mg2+.•A partial dehydration model was proposed to discuss the separation mechanism of cations in S-ED process.
Tea is the world＇s oldest and most popular caffeine-containing beverage with immense economic, medicinal, and cultural importance. Here, we present the first high-quality nucleotide sequence of the ...repeat-rich （80.9%）, 3.02-Gb genome of the cultivated tea tree Camellia sinensis. We show that an extraordinarily large genome size of tea tree is resulted from the slow, steady, and long-term amplification of a few LTR retrotransposon families. In addition to a recent whole-genome duplication event, lineage-specific expansions of genes associated with flavonoid metabolic biosynthesis were discovered, which enhance catechin production, terpene enzyme activation, and stress tolerance, important features for tea flavor and adaptation. We demonstrate an independent and rapid evolution of the tea caffeine synthesis pathway relative to cacao and coffee. A comparative study among 25 Camellia species revealed that higher expression levels of most flavonoid- and caffeinebut not theanine-related genes contribute to the increased production of catechins and caffeine and thus enhance tea-processing suitability and tea quality. These novel findings pave the way for further metabolomic and functional genomic refinement of characteristic biosynthesis pathways and will help develop a more diversified set of tea flavors that would eventually satisfy and attract more tea drinkers worldwide.
Group 4 metal-based metal–organic frameworks (MIV-MOFs), including Ti-, Zr-, and Hf-based MOFs, are one of the most attractive classes of MOF materials owing to their superior chemical stability and ...structural tunability. Despite being a relatively new field, MIV-MOFs have attracted significant research attention in the past few years, leading to exciting advances in syntheses and applications. In this outlook, we start with a brief overview of the history and current status of MIV-MOFs, emphasizing the challenges encountered in their syntheses. The unique properties of MIV-MOFs are discussed, including their high chemical stability and strong tolerance toward defects. Particular emphasis is placed on defect engineering in Zr-MOFs which offers additional routes to tailor their functions. Photocatalysis of MIV-MOF is introduced as a representative example of their emerging applications. Finally, we conclude with the perspective of new opportunities in synthesis and defect engineering.
Comprehensive Summary
5‐Methylcytosine (5mC) is a dynamic and reversible epigenetic modification in genomic DNA of higher eukaryotes. It has been well‐established that the demethylation of 5mC occurs ...through the ten‐eleven translocation (TET)‐mediated oxidation of 5mC followed by thymine DNA glycosylase (TDG)‐initiated base excision repair (BER). Recent findings also have identified an alternative pathway of DNA demethylation. In this pathway, TET enzymes directly oxidize 5mC to form 5‐formylcytosine (5fC) or 5‐carboxylcytosine (5caC). These modified bases can undergo direct deformylation or decarboxylation, respectively. Additionally, DNA demethylation can also occur through the deamination of 5mC and 5hmC, resulting in the production of thymine and 5‐hydroxymethyluracil (5hmU), respectively. Various DNA demethylation pathways possess critical functional implications and roles in biological processes. This Recent Advances article will focus on the studies of mechanisms and biological functions of DNA demethylation, shedding light on the reversible nature of the epigenetic modification of 5mC.
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