•MOF-on-MOF hybrids exhibit distinctive properties compared to single MOF.•This is the first review dedicated to the advances of MOF-on-MOF hybrids.•The synthetic strategies and structures of ...MOF-on-MOF hybrids are presented.•The potentials of MOF-on-MOF hybrids in selected applications are demonstrated.•Challenges and future directions of MOF-on-MOF hybrids are discussed.
Metal-organic frameworks (MOFs) are a promising class of porous crystalline materials with diverse applications, the properties of which are dependent on their structures including both compositions and architectures. The intensive research of MOFs has led to an emerging family of MOF-on-MOF hybrid materials constructed by the conjugation of two or more MOFs units. The advances in the field of MOFs have been summarized in numerous excellent reviews on single MOFs, MOFs-based composites via conjugation with non-MOF materials and their derivates. However, there is a lack of dedicated review on MOF-on-MOF hybrids. Within this context, herein we provide a timely and comprehensive summary on the achievements of MOF-on-MOF hybrids. An introduction of the synthetic strategy/formation mechanism is firstly presented to explain the interaction between host and guest MOFs. Then, the structural diversity in MOF-on-MOF systems is discussed in detail to demonstrate how MOF-on-MOF hybrid systems enable advances in various applications. Finally, challenges and future directions of MOF-on-MOF development are described as our own perspectives.
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•MOFs based on Polyethyleneimine (PEI) and Ce(NO3)3 as biomaterial were prepared.•PEI-Ce(III) MOFs possess <0.5% hemolysis, and >90% blood clotting index values.•P-PEI-Ce(NO3)3 MOFs ...with antibacterial, and antioxidant properties are attained.•PEI-based MOFs are promising and adaptable multipurpose material in biomedicine.
Here, a well-known antibacterial cationic branched polyethyleneimine (PEI) is used as organic linker in the preparation of metal organic frameworks (MOFs) with a lanthanide salt, Cerium (III) nitrate (Ce(NO3)3) for two types of MOFs. One of the MOF is PEI-Ce(III) prepared from the aqueous solutions of PEI and Ce (III) ions at room temperature. The second MOF is prepared from the HCl treated PEI (p-PEI) and Ce(NO3)3 in ethanol as p-PEI-Ce(NO3)3 MOFs. The MOFs are prepared at 1: 0.25, 1:0.5 and 1:1 mol ratios of PEI repeating unit to Ce(III) ions and named as p-PEI-Ce(NO3)3–0.25, −0.5, and −1, respectively. The prepared PEI-Ce(III) MOFs are in powder form, whereas p-PEI-Ce(NO3)3 MOFs are sticky and viscous as gum and soluble in water. The surface areas of PEI-Ce(III) MOFs are found to decrease with the increase in the amount Ce(III) amount and maximum surface area is measured for PEI-Ce(III)-0.25 as 142.3 m2/g, while the surface area of p-PEI-Ce(NO3)3 MOFs cannot be measured. Additionally, all the PEI-Ce(III) MOFs are found blood compatible with < 0.5% hemolysis and >90% blood clotting index values up to 0.25 mg/mL concentration. Also, the antioxidant activity of PEI which is 1107 ± 26 Trolox Equivalent Antioxidant Capacity (TEAC mM/g) is retained as 166 ± 12, 186 ± 1.0, 194 ± 2.0 for p-PEI-Ce(NO3)3–0.25, −0.5, and −1 MOFs, respectively whereas no antioxidant activity in for Ce(III) is measured at the same concentrations. More importantly, the antimicrobial activity of PEI that is measured by via both micro-dilution and disc diffusion antimicrobial tests is also maintained for p-PEI-Ce(NO3)3 MOFs against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, and Candida albicans with the MIC values ranging 0.625–5.0 mg/mL and the MBC values of 1.25–10 mg/mL.
•We reviewed the application of MOF materials in removal of Hg2+ ions.•We described the advantages of MOF membrane in removal of Hg2+ ions.•We propose the current problems faced by Hg2+ ions ...treatment and future solutions.
Mercury pollution of water has caused serious health problems in humans. Therefore, reducing the mercury content into the drinking water standard is currently a priority measure. As a kind of porous frame materials with adjustable structure and easy to design and synthesize, metal–organic frameworks (MOFs) materials have attracted widespread attention. Their large specific surface area and adjustable pores make MOFs an excellent platform for removing mercury metals from water. In this review, we discussed the mercury removal performance of functionalized MOF powder materials, including sulfur-functionalized MOF, nitrogen-functionalized MOF, nitrogen-sulfur co-functionalized MOF, MOF composites and MOFs-derived materials. Compared to MOF powder materials, MOF membranes can easily recycle and effectively avoid secondary pollution. Therefore, we also reviewed nanofiber MOF membranes and polymer-supported MOF membranes. At the same time, in order to further explore the potential of MOF materials in heavy metal adsorption, we also introduced the current problems and challenges faced by MOF materials in detail, and proposed future research directions and difficulties to be overcome. We will hope that the review may provide more researchers with a more comprehensive, intuitive, clear cognition.
The immoderate use of pesticides in the modern agricultural industry has led to the pollution of water resources and ultimately threatens the human body. Herein, two metal–organic frameworks (MOFs), ...namely {Zn(tpt)2·2H2O}n (Zn1) and {Zn2(tpt)2(bdc)}n (Zn2), (Htpt = 5‐4(1H‐1,2,4‐triazol‐1‐yl)phenyl‐2H‐tetrazole), respectively, are constructed as smart materials for visual and on‐site detection of pesticides and their removal from water. The exposed nitrogen‐rich sites and high chemical stability make Zn2 a self‐assembly core to further fabricate MOF‐on‐MOF‐sodium alginate (ZIF‐8‐on‐Zn2@SA) composite by wrapping ZIF‐8 on the outside surface. Inheriting the excellent fluorescent emission of Zn2, the rod‐like ZIF‐8‐on‐Zn2@SA module exhibits naked‐eye detection of thiophanate‐methyl (TM) in real fruits and vegetables with a broad linear range (10–100 × 10−6 m), a low limit of detection (LOD = 0.14 × 10−6 m), and satisfactory recoveries (98.30–102.70%). In addition, carbendazim (CBZ), the metabolite of TM after usage in crops, can be efficiently removed from water by the ZIF‐8‐on‐Zn2@SA (qmax = 161.8 mg g−1) with a high correlation coefficient (R2 > 0.99). Therefore, the portable ZIF‐8‐on‐Zn2@SA sensing platform presents a promising candidate for monitoring and removal of pesticides, especially suitable for regions with serious pesticide environmental pollution.
Through coordination chemistry theory, a practicability and portable ZIF‐8‐on‐Zn2@SA hydrogel is designed and constructed based on a 3D metal–organic framework (Zn2) for naked‐eye detection and effective removal of pesticides.
Typical illustration representing the citrate capped magnetite and UiO-66-NH2 composite towards dual green applications of Cr (VI) adsorption and photocatalytic hydrogen evolution.
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...Design and facile fabrication of a magnetically separable hetero-structure photocatalyst as well as an adsorbent having dual green benefits towards energy conversion and pollutant remediation are quite indispensable in the current scenario. In this regard, a composite of citrate capped Fe3O4 and UiO-66-NH2 has been designed to remediate Cr (VI) by adsorption and harvest photons from visible light for clean energy (H2) conversion. The material was prepared by the union of citrate capped Fe3O4 (CCM) and versatile aqueous stable Zr-based MOF (UiO-66-NH2) through in-situ solvothermal method. The composite of CCM with MOF (MU-2) was studied through sophisticated analysis techniques; PXRD, FT-IR, BET, UV–Visible DRS, PL, TG, HRTEM and XPS etc. to reveal the inherent characteristics of the material. BET surface analysis revealed high specific surface area (572.13 m2 g−1) of MU-2 in comparison to its pristine MOF. Furthermore, the dual function composite MU-2′s VSM studies showed that its magnetic saturation is 3.07 emu g−1 that is suitable for magnetic separation after desired reaction from aqueous media. The Cr (VI) sorption studies revealed that the composite adsorbent (MU-2) showed maximum monolayer adsorption capacity (Qm) of 743 mg g−1 which followed pseudo second order kinetics. Moreover, the sorption thermodynamics revealed that the process was spontaneous and endothermic in nature. In addition to it, the synthesized composite material displayed enhanced activity towards photocatalytic H2 evolution with a maximum evolution rate of 417 µmole h−1 with an apparent conversion efficiency (ACE) of 3.12 %. Typically, MU-2 displays high adsorptions of Cr (VI) as well as some extent of Cr (VI) reduction owning to its populous active sites and free carboxylate groups respectively. Moreover, the synergistic effect of CCM and UNH in the composite resulted in Z scheme mediated charge transfer mechanism that showed enhanced H2 photo-evolution rates. Hence, MU-2 can be readily utilized as magnetically retrievable dual function composite for Cr (VI) adsorption and photocatalytic H2 evolution.
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•Ultrasound/Fenton system was firstly explored for the application of Fe-MOFs.•There was a synergistic effect between ultrasound and Fenton processes.•The TC-HCl could be effectively ...removed in a wide range of pH (5–11).•OH was generated by the unsaturated iron sites, cavitation effect and H2O2 decomposition.•OH and O2– both contributed to the degradation, while ·OH contributed more.
In this work, as a new strategy, ultrasound/H2O2/MOF system was firstly applied by environmental-benign Fe-MOFs (MIL-53, MIL-88B and MIL-101) for tetracycline hydrochloride removal. The syntheticFe-MOFs were characterized by XRD, FTIR, SEM, XPS, N2 sorption-desorption isotherms and CO-FTIR. MIL-88B demonstrated the best catalytic performance because of its highest amount of Lewis acid sites. Influencing factors, contrast experiment, and corresponding dynamics were carried out to obtain the best experimental conditions and reaction system. Under optimal conditions (Tetracyclinehydrochloride = 10 mg/L, MIL-88B = 0.3 g/L, H2O2 = 44 mM, ultrasound power = 60 W, and pH = 5.0), the-first-order kinetic rate constant k was calculated to be 0.226 min−1, higher than the simple combination of the ultrasound system (0.004) and MIL-88B/H2O2 system (0.163), indicating the importance of synergistic effect between ultrasound and Fenton reaction. EPR test and quenching experiment proved that ·OH is mainly responsible for tetracycline hydrochloride removal. The major reaction path is the adsorption and decomposition of H2O2 by coordinative unsaturated iron sites on Fe-MOF, but it is not the only path. The direct decomposition of H2O2 and the cavitation effect caused by ultrasound also contribute to the generation of OH.
•Partially converted MOFs can well integrate the structural superiorities of pristine MOFs and MOF derivatives in one entity.•This is the first review dedicated to the advances of PC-MOFs.•The ...synthetic strategies and achieved structures of PC-MOFs are summarized.•The structural superiorities of PC-MOFs in catalysis and energy storage/conversion are demonstrated.•Challenges and future directions of PC-MOFs are prospected.
Partially converted metal–organic frameworks (PC-MOFs), an emerging class of MOF composite materials, are synthesized by partial conversion of the metals and/or ligands in pristine MOFs into functional derivatives with the skeletons of MOFs partially preserved. As a bridge between currently predominate MOFs and completely converted MOF derivatives, PC-MOFs with integrated structural merits and unexpected new properties have received increasing attention. Herein, a timely review on the latest advances and breakthroughs in the synthesis and applications of PC-MOFs is presented. Firstly, the synthetic routes and conversion mechanisms are summarized to introduce how to realize partial conversion of MOFs to PC-MOFs with controllable structures and compositions. Secondly, the enhanced performance of PC-MOFs in catalysis and energy related fields are highlighted to demonstrate the structural superiorities. Finally, our perspectives on the current challenges and future directions are provided, aiming to inspire the further developments in the field of PC-MOFs.
Metal-organic frameworks (MOFs) with 3D structure and tunable composition can provide more electrochemical active sites for redox reactions. They are expected to achieve stable cycles for reversible ...sodium ion storage. In this work, a novel spitball-like anode material for sodium-ion batteries (SIBs) has been prepared by a facile solvothermal method followed by the spray drying, in which the reduced graphene oxide (RGO) is coated on the composite of cobalt hydroxidenitrate (Co3(NO3)2(OH)4) combined with the zircomiun based MOFs (Zr-MOF). The combination of Co3(NO3)2(OH)4 with Zr-MOF can not only improve the structural stability but also enlarge the specific surface area of anode materials. Meanwhile, the coating of spitball RGO can further improve the electric conductivity and the cycling stability of Co3(NO3)2(OH)4@Zr-MOF composite effectively. As a result, such a composite anode can exhibit a high reversible capacity of 555 mAh g−1 at 0.1 A g−1 as well as a capacity retention ratio of 94.3% with discharge capacity of 525 mAh g−1 after 100 cycles. Notably, the Co3(NO3)2(OH)4@Zr-MOF@RGO anode can also deliver a high-rate capacity of 340 mAh g−1 at 1 A g−1. These results suggest that the Co3(NO3)2(OH)4@Zr-MOF@RGO material is a promising anode to build the high-rate and long-life SIBs.
•The Zr-MOF improves the structural stability of active materials during cycling.•The RGO coating results in the lower consumption of electrolyte and increases the ICE.•The Co3(NO3)2(OH)4@Zr-MOF@RGO anode exhibits stable cycle performance for SIBs.
Combining different metal−organic frameworks (MOFs) into a conjugate material can integrate the properties of each MOF component and further lead to emergent properties from the synergistic ...heterostructured units. In this work, two kinds of bimetallic TbFe-MOFs have been designed by MOF-on-MOF strategy and utilized as a platform for anchoring carbohydrate antigen 125 (CA125) aptamer to detect CA125 and living michigan cancer foundation-7 (MCF-7) cells. Although the integrated MOF-on-MOF architectures show similar chemical and structural features to that of the top layer, the Fe-MOF-on-Tb-MOF and Tb-MOF-on-Fe-MOF have different surface nanostructures to their parent MOFs. The developed aptasensor based on Tb-MOF-on-Fe-MOF displays higher stability of the formed G-quadruplex between aptamer and CA125 than that based on Fe-MOF-on-Tb-MOF, owing to stronger immobilization behavior of the aptamer for the Tb-MOF-on-Fe-MOF composite. The developed aptasensor provides an extremely low detection limit of 58 μU·mL−1 towards CA125 within a wide linear range from 100 μU·mL−1 to 200 U·mL−1, which is significantly lower than those of all reported sensors. This aptasensor also has high selectivity, good stability, acceptable reproducibility, and excellent applicability in human serum. Moreover, the Tb-MOF-on-Fe-MOF nanoarchitecture demonstrates superior biocompatibility and good endocytosis. As a result, the developed aptasensor illustrates high sensitivity for detection of MCF-7 cells with an extremely low detection limit of 19 cell·mL−1. Therefore, the proposed aptasensor based on Tb-MOF-on-Fe-MOF exhibits great potentials for early diagnosis of tumors.
•Bimetallic FeTb-MOFs obtained by using the MOF-on-MOF strategy.•Novel platform for the CA 125 RNA aptamer immobilization, detection of CA 125 and living cancer cells.•Excellent biocompatibility, good endocytosis, and strong fluorescence of Tb-MOF-on-Fe-MOF.•Ultra-low detection limit and other sensing performances.
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