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The development of confined growth of metal-organic frameworks (MOFs) in a nano-space remains a challenge mainly due to the spatial size randomness and inhomogeneity of host materials and the limitation of MOF species. In this study, we developed a general "stepwise vacuum evaporation" strategy, which allows the nano-confined growth of MOFs in hollow mesoporous silica nanospheres (HMSN) by the vacuum forces and the capillary effect. A series of nanoscale MOFs including ZIF-8, ZIF-90, HKUST-1, MIL-53(Cr) and UiO-66-NH

Photo-functionalized metal–organic frameworks with unique structures and rich fluorescent components exhibit different levels of optical anti-counterfeiting under various types of stimulation.

Visible-light-driven organic transformation photocatalyzed by metal-organic frameworks (MOFs) under mild conditions is considered a feasible route to conserve energy and simplify synthesis. Herein, a light-sensitized, three-dimensional uranyl-organic framework (

Solar-driven interface water evaporation has shown great potential in seawater desalination. A solar steam generation device with excellent performance requires materials that can efficiently absorb solar energy to achieve photothermal conversion. ZIF-L (a Co-based metal–organic framework) after carbonization has the dual role of carbon nanoplates and cobalt nanoparticles to absorb solar light, exhibiting broad light absorption. Herein, based on carbonized ZIF-L and natural wood, we designed a solar-driven interface water evaporation device, in which ZIF-L after carbonization is used to achieve photothermal conversion, and wood aerogel with high porosity is used as a supporting layer to transport seawater to the evaporation interface and realize self-floating of the device. The prepared evaporator exhibited a high evaporation rate of 1.52 kg m−2 h−1 and an evaporation efficiency of 92.42% under 1 sun illumination, and neither salt accumulation nor a significant decrease in the evaporation rate of the device was observed after continuous operation for 10 evaporation cycles. Additionally, the excellent resistance to salt deposition and automatic salt discharge ability of the evaporator were demonstrated, which can ensure its long-term stable operation. The high-efficiency and stable evaporation performance demonstrate the evaporator's great potential in the practical application of solar energy production of clean water.

Cr(VI) is a type of dangerous effluent that has caused great harm to human health and the environment. Recognition and perception of Cr(VI) by artificial receptors has attracted extensive attention. A novel fluorescent chemical sensor based on the 5,7-dihydroxyflavone skeleton was designed and synthesized for the selective recognition of Cr(VI). As confirmed by fluorescence technology, the fluorescent probe 4-dimethylaminobenzyl chrysin ester-Zn (DBC-Zn) showed high sensitivity and selectivity for dichromate and a fast response (less than 30 sec) recognition. The fluorescence intensity of DBC-Zn varies linearly with the concentration of Cr(VI) in the range 0.1-1 μM. The detection limit of Cr2 O7 2- by DBC-Zn is 2.3 nM, which is far lower than the national safe drinking water standard stipulated by the US Environmental Protection Agency (1.9 μM). The quenching mechanism of the probe can be attributed to the interaction of the dynamic quenching effect and the fluorescence internal filtration effect. In addition, the probe has good stability in both neutral and alkaline environments, and the accuracy of quantitative analysis of Cr2 O7 2- in lake water or tap water is more than 80%. The test paper based on DBC-Zn can effectively detect Cr2 O7 2- at the concentration of 100 ppb. This shows that the probe has a certain practical application value.

Interface solar-driven evaporation is a very promising technology used in solar energy harvesting, seawater desalination and water purification. However, salt accumulation is still a serious problem that hinders the long-term stable operation of the evaporator. Herein, we use natural wood with inherent porosity to develop a flexible cellulose aerogel, which can be used as efficient and stable solar evaporator for desalination after simple surface carbonization. This aerogel evaporator achieves a solar steam efficiency of 83.4% and an evaporation rate of 1.40 kg m−2 h−1 under the sunlight intensity of 1 kW m−2. In the simulated evaporation experiment for 7 days, the evaporator shows a stable evaporation rate (about 1.39 kg m−2 h−1), indicating the potential for long-term operation. In addition, the evaporator has the ability to resist salt accumulation and self-cleaning. The low cost, simple preparation and multiple functions make the evaporator promising to be a continuous and stable installation for solar desalination.

The phenomenon of single-crystal to single-crystal transformation and the performance change along with the transformation have been widely discovered, whereas the efficient utilization of the crystal transformation process is less reported. Herein, we present an interesting thermally driven single-crystal to single-crystal transformation of HNU-43. During transformation, the effective encapsulation of camptothecin (CPT) has been achieved as CPT-HNU-43 converts into CPT-HNU-43(T), which cannot directly encapsulate CPT owing to the small channel size of HNU-43(T). Following the successful packaging, the CPT can be triggered to gradually release as pH = 6.0 which is quite close to the acid environment of cancer cells. Furthermore, CPT-HNU-43(T) nanoparticles show excellent biocompatibility, and the cancer cells can be effectively inhibited through the release of CPT.

Recently, highly porous metal–organic frameworks (MOFs), with excellent porosity and abundant functional groups, have represented a new addition to the area of capturing uranium ion pollutants. To achieve high adsorption capacity and removal efficiency of uranium, it is significant to modify the morphology of MOF-based adsorbents. In this contribution, two hollow structured ZIF-8 adsorbents were used for the adsorptive separation of uranium from aqueous solution. Both of them showed faster adsorption rate and larger adsorption capacity than pristine ZIF-8, providing the prospect of hollow MOF materials to the application of uranium extraction.

As an important factor affecting global agricultural output, pesticides have a significant impact on the ecosystem. It is an urgent task to accurately and conveniently detect pesticide residues after their application. Herein, a fluorescent dye@MOF platform was designed via the encapsulation of rhodamine B (RhB) into the MOF structure (named RhB@

The composite of CdTe quantum dots (QDs) with ZIF-8 was elaborately designed and synthesized as an enzyme-free fluorescent probe for the sensitive determination of uric acid (UA), based on the fluorescence detection property of CdTe QDs and the signal amplification function of ZIF-8. The structure and feature of the composite were characterized with transmission electron microscopy, scanning electron microscopy, powder X-ray diffraction, and fluorescence spectrometry. With adding UA to the composite, the emission of CdTe QDs reduced due to the inner filter and dynamic quenching effects of UA, and the adsorption ability of ZIF-8 toward UA promoted the response signal of CdTe QDs. On this basis, UA was quantified by the composite in the concentration range 0.05 to 10 μM with excitation/emission wavelength at 287/615 nm, and the detection limit of the composite toward UA was 32 nM. The reproducibility of the composite for determining UA was further evaluated, and the relative standard deviations were below 10.2%. The composite also exhibited the merits of enzyme-free analysis such as low testing cost, short analysis time (1 min), and loose pH condition (application in whole physiological pH range, 5.0 - 8.0). The composite was applied to the determination of UA in human urine with recoveries of spiked samples in the range 99 to 113%.

The presence of stable U(V)-containing compounds is important for the study of radionuclides. However, pentavalent uranium is prone to disproportionation, thus U(V)-containing compounds are generally sensitive to air and water. Herein, a stable mixed-valent uranium (U(V)/U(VI))-based metal–organic framework was synthesized via an in situ hydrothermal method, which features a three-dimensional structure with 3-fold interpenetration. Moreover, it can be used as a dual-responsive fluorescence temperature sensor based on the fluorescence intensity and fluorescence lifetime in the cryogenic range of 77–197 K. The fluorescence enhancement at low temperature (77 K) is about 25 times higher that at room temperature, which is unparalleled in common fluorescent materials. The mechanism can be interpreted as the decrease of nonradiative decay with decreasing temperature. Overall, this finding is beneficial to further our understanding of actinides in this oxidation state and disclose their potential applications.

Green and clean energy technologies, including fuel cells, metal-air batteries, water splitting et al., are becoming more significant for our lives. Oxygen reduction reaction (ORR), hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are key reaction processes for fuel cells, metal-air batteries and water splitting. Therefore, it is highly desirable to design a multifunctional catalyst, which owns catalytic performance under a widely applied range. Herein, we demonstrate a novel multifunctional catalyst (Co/Co3O4@C) by carbonizing a composite material constructed of zeolite imidazolate framework and carbon fiber paper (ZIF-L-Co@CP). It is a carbon-based material containing metallic Co and Co3O4 as a low-cost and effective catalyst toward the ORR and overall water splitting. For ORR, the Co/Co3O4@C catalyst shows high half-wave potential in both alkaline and acidic media, 0.823 V for 0.1 M KOH and 0.672 V for 0.1 M HClO4. More importantly, it exhibits good catalytic activities of hydrogen and oxygen evolutions to perform overall splitting in actual seawater.

Systematic design and self-assembly of metal-organic polyhedra with predictable configuration has been a long-standing challenge in crystal engineering due to the difficulty of finding suitable building units. Herein, we are focused on a concave polyoxovanadate cluster [V6O6(OCH3)9(SO4)4]5- that can be generated in situ under the exact reaction conditions. Based on this cluster, a potential trivalent molecular building block [V6O6(OCH3)9(SO4)(CO2)3]2- can be obtained by the bridging-ligand-substitution strategy that possesses appropriate angle information for the design of molecular cubes. Utilizing the face-directed assembly of the trivalent molecular building block and a diverse set of tetratopic carboxylate linkers, a series of metal-organic cubes VMOC-1 to VMOC-5 with the same topology but different functionalities and dimensions are designed and constructed. The inclusion study made with VMOC-3 as an example has shown that they are potential molecular receptors and can selectively capture size-matching polycyclic aromatic hydrocarbon guest molecules.

A new fluorescent supramolecular organic framework (HNU-35) has been constructed, which is a three-dimensional structure composed of hydrogen bonding interactions between the carboxyl groups of adj...

Uranium is one of the principal raw materials in the nuclear industry, but if released into the natural environment, it also poses latent health risks to mankind. Therefore, there is an urgent need to develop a strategy that can concurrently detect and adsorb uranium to realize the sustainable development of nuclear power and protect the environment. In this work, a fluorescent zinc-based metal-organic framework (HNU-50) was designed and synthesized for the effective detection and extraction of U(VI). The amide groups on N-pyridin-4-ylpyridine-4-carboxamide ligands and two uncoordinated carboxyl oxygen atoms on pyromellitic acid ligands in HNU-50 provide potential uranium-binding sites. Consequently, HNU-50 is competent of selectively and efficiently catching uranyl ions, achieving an optimum adsorption capacity of 632 mg/g. Additionally, the adsorption of U(VI) results in fluorescence quenching of HNU-50, thus allowing sensitive and selective detection of U(VI) by fluorescence change. Note that HNU-50 exhibits a considerably low detection limit of 1.2 × 10-8 M for U(VI) in aqueous solution, which is below the World Health Organization maximum pollution standards for potable water (6.3 × 10-8 M).

A reverse-binding-selectivity between monovalent and divalent cations was observed for two different self-assembly G(16)-hexadecamer and G(8)-octamer systems.The dissociation constant between G(4)-quadruplex and monomer was calculated via VT-(1)H NMR experiments. Quantitative energy profiles revealed entropy as the key factor for the weaker binding toward Ba(2+) compared with K(+) in the G(8)-octamer system despite stronger ion-dipole interactions. This study is the first direct comparison of the G(4)-quartet binding affinity between mono and divalent cations and will benefit future applications of G-quadruplex-related research. Further competition experiments between the G(8)-octamer and 18-crown-6 with K(+) demonstrated the potential of this G(8) system as a new potassium receptor.

The core–shell/yolk–shell/hollow structures of nanoparticles have attracted considerable attention due to their wide applications in various fields. Herein, we have successfully developed a facile strategy for the controlled synthesis of core–shell/yolk–shell/hollow structured ZIF-67@Co-LDH/SiO2 by using zeolitic imidazolate framework-67 (ZIF-67) as a self-sacrificing template. The mesoporous core–shell/yolk–shell/hollow nanostructured ZIF-67@Co-LDH/SiO2 material was obtained by controlling the reaction time under the protection of hexadecyltrimethylammonium bromide. In this research, SEM, TEM and PXRD were used to characterize the morphology, size, composition and structure of the obtained ZIF-67@Co-LDH/SiO2 material. The formation mechanism of the core–shell/yolk–shell/hollow structures was elucidated. Moreover, the unique structural characteristics and porosity enable the prepared core–shell/yolk–shell/hollow nanostructure ZIF-67@Co-LDH/SiO2 to exhibit good adsorption performance for Congo red.

Recent years have witnessed a rapid development of fluorescent probes in both analytical sensing and optical imaging. Enormous efforts have been devoted to the regulation of fluorescent probes during their development, such as improving accuracy, sensitivity, selectivity, recyclability and overcoming the aggregation-caused quenching effect. Metal-organic frameworks (MOFs) as a new class of crystalline porous materials possess abundant host-guest chemistry, based on which they display a great application potential in regulating fluorescent probes. This review summarized the research works on the regulation of fluorescent probes using MOFs, with emphasis on the methods of integrating fluorescent probes into MOFs, the regulation effects of MOFs on fluorescent probes, the superiorities of MOFs in regulating fluorescent probes, and the outlook of this subject. It is desirably hoped that this review can provide a useful reference for the researchers interested in this field.