UiO-type Metal-organic Frameworks Research Articles

Guest-responsive coherence time of radical qubits in a metal-organic framework.

Metal-organic frameworks (MOFs) integrated with molecular qubits are promising for quantum sensing. In this study, a new UiO-type MOF with a 5,12-diazatetracene (DAT)-containing ligand is synthesized, and the radicals generated in the MOF exhibit high stability and a relatively long coherence time (T2) responsive to the introduction of various guest molecules.

Partial-Interpenetration-Controlled UiO-Type Metal-Organic Framework and its Catalytic Activity.

An unprecedented correlation between the catalytic activity of a Zr-based UiO-type metal-organic framework (MOF) and its degree of interpenetration (DOI) is reported. The DOI of an MOF is hard to control owing to the high-energy penalty required to construct a partially interpenetrated structure. Surprisingly, strong interactions between building blocks (inter-ligand hydrogen bonding) facilitate the formation of partially interpenetrated structures under carefully regulated synthesis conditions. Moreover, catalytic conversion rates for cyanosilylation and Knoevenagel condensation reactions are found to be proportional to the DOI of the MOF. Among MOFs with DOIs in the 0-100% range, that with a DOI of 87% is the most catalytically active. Framework interpenetration is known to lower catalytic performance by impeding reactant diffusion. A higher effective reactant concentration due to tight inclusion in the interpenetrated region is possibly responsible for this inverted result.

Precise Regulation of the Coordination Environment of Single Co(II) Sites in a Metal–Organic Framework for Boosting CO2 Photoreduction

While the coordination environment around catalytic metal sites plays a crucial role in catalysis, its precise design and modulation still remain a challenge. Herein, the coordinated N atom number around single Co sites installed on a UiO-type metal–organic framework has been modulated to afford UiO-Co-Nx (x = 2, 3, and 4) for photocatalytic CO2 reduction. Significantly, the photocatalytic performance is affected by the coordinated N atom number around the Co site, in which UiO-Co-N3 exhibits superior activity to the other counterparts. Photo-/electrochemical results support the fastest charge transfer kinetics between the photosensitizer and UiO-Co-N3. Theoretical calculations, together with the results acquired from in situ diffuse reflectance infrared Fourier transform spectra, manifest the lowest energy barriers of the rate-determining step and desorption energy of CO* over UiO-Co-N3 among all UiO-Co-Nx samples.

Quantification of Linker Defects in UiO-Type Metal–Organic Frameworks

Quantification of Linker Defects in UiO-Type Metal–Organic Frameworks

Solid-phase rapid synthesis of hierarchical UiO-type metal-organic frameworks as excellent solid acid catalysts for acetalization of benzaldehyde with alcohol.

Functionalized metal-organic frameworks (MOFs) have been used in a wide range of applications. Although the development of functionalized MOFs with plentiful open metal sites (defects) provides an avenue for targeted reactions, creating such defects remains challenging. Herein, a UiO-type MOF with hierarchical porosity and plentiful Zr-OH/OH2 sites (capping 35% Zr coordination sites) was synthesized within 40 min by a solid-phase synthesis route without the use of solvent and template. The optimal sample converted 5.7 mmol benzaldehyde to (dimethoxymethyl)benzene within 2 min at 25 °C. The turnover frequency number and activity per unit mass reached 2380 h-1 and 8568 mmol g-1 h-1, respectively, outperforming all previously reported catalysts at room temperature. This excellent catalytic activity was correlated with the defect density in functionalized UiO-66(Zr) and the accessibility of plentiful Zr-OH/OH2 sites as acid sites.

Systematic evaluation of water adsorption in isoreticular UiO-type metal–organic frameworks

A systematic investigation on structure–property relationships of water adsorption was realized in isomorphic UiO-type MOFs, revealing that functionalizing MOFs with N sites may provide a strategy to improve low-pressure water uptakes and kinetics.

Synthesis and Catalytic Activity in the Hydrogenation Reaction of Palladium-Doped Metal-Organic Frameworks Based on Oxo-Centered Zirconium Complexes

Metal-nanocluster-doped porous composite materials are attracting considerable research attention, due to their specific catalytic performance. Here we report a simple, cheap, and efficient strategy for the preparation of palladium hydrogenation catalysts based on metal-organic frameworks (MOFs). It has been shown that the synthesis of Pd/MOF results in the formation of palladium nanoparticles uniformly fixed on the surface. The composition and structure of the resulting composites were studied using elemental analysis, DSC, TGA, XRD, TEM, and IR spectroscopy. Pd nanoparticles with an average diameter of 8–12 nm were successfully confined in the UiO-type MOFs, and the obtained nanocomposites exhibited abundant porosity, high stability, and a large surface area. It has been shown that the resulting catalytic systems with high activity, selectivity, and stability reduce phenylacetylene and allyl alcohol to styrene and propanol, respectively, in liquid-phase hydrogenation reactions.

Embedding Multiphoton Active Units within Metal-Organic Frameworks for Turning on High-Order Multiphoton Excited Fluorescence for Bioimaging.

The fabrication of high-order multiphoton excited fluorescent materials for second near-infrared (NIR-II, 1000-1700 nm) light-induced fluorescence imaging has always been an intractable challenge. In this study, a reasonable strategy guided by theoretical calculations was employed to fabricate a novel high-order multiphoton excited fluorescence (H-MPEF)-responsive UiO-type metal-organic framework (MOF, ZrTc). Strategically, the functionalization of the photonic-responsive thiazolothiazole-based organic ligand gave rise to amplified H-MPEF (four-photon activity) performance and prolonged excitation wavelength (1550 nm) of ZrTcI. The results reveal that the extended π-electron system, enhanced charge transfer, improved dipole moment, and weakened π-π stacking interactions within the MOFs endow them with excellent H-MPEF performance for NIR-II light-induced fluorescence imaging. It is an extremely rare report on H-MPEF bioimaging using MOFs and provide a universal strategy for the fabrication of H-MPEF-responsive materials.

Solid-Phase Rapid Synthesis of Uio-Type Metal Organic Framework with Hierarchical Porosity and Excellent Catalytic Performance in Aldol Reaction

Solid-Phase Rapid Synthesis of Uio-Type Metal Organic Framework with Hierarchical Porosity and Excellent Catalytic Performance in Aldol Reaction

MOF nanoparticles as heterogeneous catalysts for direct amide bond formations.

The influence of composition and textural characteristics of a family of ultra-small isoreticular UiO-type metal-organic frameworks (MOFs) with different functionalized and extended linkers on their catalytic performance is evaluated. Two direct amide bond formations across four different substrates (benzylamine + phenylacetic acid and aniline + formic acid) are employed as proof-of-concept reactions to test the activity of the Zr-MOF nanoparticles. The reaction rates of amide bond formation are evaluated against physico-chemical properties such as crystallinity, porosity, particle size or linker functionality, alongside the Lewis acid and hydrophobic properties of the MOFs, in order to gain insights into the catalytic mechanism and optimal properties for its enhancement.

Dual-functional UiO-type metal-organic frameworks for the sensitive sensing and effective removal of nitrofurans from water

Herein, a dual-functional platform for simultaneous detection and removal of Nitrofurans (NFs), a class of widely used antibiotics, from aqueous solution is developed on the basis of water-stable luminescent UiO-Type Metal-Organic Frameworks (Zr-fcu-sti). Specifically, Zr-fcu-sti responds to NFs at parts per billion (ppb) levels based on the efficient luminescence quenching and is one of the most sensitive luminescent MOF-based sensing materials. The efficient luminescence quenching can be explained by a combined effect of the strong absorption of NFs at the excitation wavelength and the photo-induced electron transfer process from the ligand of Zr-fcu-sti to NFs. In addition, NFs can obviously cause the red shift of the probe's maximum emission, which can be used as an indicator for the qualitative detection of NFs, clearly distinguishing them from other types of antibiotics. Meanwhile, its suitable pore size, large surface areas and the widely distributed hydrogen bonding sites on pore surfaces endow the MOF with excellent uptake capacity toward NFs in aqueous environment. These results show that, as a water-stable dual-functional material with great application prospects, Zr-fcu-sti can achieve high-sensitivity fluorescence sensing and efficient adsorption of NFs from water.

Cu2+-modified MOF as laccase-mimicking material for colorimetric determination and discrimination of phenolic compounds with 4-aminoantipyrine.

Based on the laccase-mimicking activity of Cu2+-modified University of Oslo (UiO) metal-organic framework (UiO-67-Cu2+), we developed acolorimetric sensor array for distinguishing a series of phenols with different number and position of substituted hydroxyl group (-OH) and different substituent group on the benzene ring, including phenol, catechol, quinol, resorcinol, pyrogallol, phloroglucinol, o-chlorophenol, o-aminophenol, and o-nitrophenol. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of phenolic compounds were obtained by theoretical calculation. The results show that the lower the LUMO energy level, the easier the chromogenic reaction occurs. The UiO-67-Cu2+-catalyzed phenol chromogenic reaction showed a good linearity in the range from 0.1 to 200μM with limit of detection approximately 61nM. Through the detection of phenol in tap water and river water, the recovery rate and RSD (n = 3) were calculated as 94.1~103% and 1.0~3.3, respectively, showing good recovery, reliable results, and outstanding stability. Therefore, the proposed colorimetric sensor array will have a great potential for the detection of phenols in the environment. Schematic presentation of a simple and sensitive colorimetric strategy based on the laccase-mimicking activity of Cu2+-modified UiO-type metal-organic framework (MOFs, Uio-67-Cu2+) to distinguish phenols with analogous structures.

A fluorescence turn-down-up detection of Cu2+ and pesticide quinalphos using carbon quantum dot integrated UiO-66-NH2

Synthesis of a fluorescent probe consisting of carbon quantum dot integrated metal–organic framework (OPCD@UiO-66-NH 2 ) via a facile one-pot route has been reported. Carbon dot derived from orthophenylenediamine (OPCD) with a PLQY (26%) has been deposited on UiO-type metal organic framework by introducing OPCD during the synthesis of MOF. The resulting fluorescent OPCD@UiO-66-NH 2 composite shows better fluorescence properties as well as photostability than pristine OPCD. The molecular interaction between UiO-66-NH 2 and Cu 2+ can be sensed by encapsulated OPCD. As a result the OPCD@UiO-66-NH 2 shows remarkable fluorescence quenching on addition of Cu 2+ . However, in presence of organophosphorus pesticide quinalphos, the fluorescence intensity (at λ 425 ) of CD@UIO-66-NH 2 is regained because of competitive binding of Cu 2+ with quinalphos and releasing OPCD@UIO-66-NH 2 to the medium. Thus a dual sensor for Cu 2+ and quinalphos can be established by measuring fluorescence intensity at λ 425 . The relative increase in fluorescence intensity for quinalphos (F/F 0 ) works linearly in the concentration range 0–16 μM and the limit of detection is found to be 0.3 nM. The specific and selective recognition of our probe towards organophosphorus pesticide quinalphos makes it suitable for real field applications. • A carbon dot integrated UiO fluorescence sensor has been designed for detection of quinalphos in aqueous medium. • The sensing mechanism is based on disruption of non-radiative CD@UiO-Cu 2+ complex in presence of quinalphos. • The limit of detection is 0.3 nM which is lowest among the published papers. • The sensors can be successfully used to detect quinalphos in real samples.

Application of hard and soft acid base theory to uncover the destructiveness of Lewis bases to UiO-66 type metal organic frameworks in aqueous solutions

Metal organic frameworks (MOFs), emerging adsorbents and catalysts in the wastewater treatment field, are subject to destruction by Lewis bases in wastewater, such as F− and PO43−.

Enzyme-Powered Porous Micromotors Built from a Hierarchical Micro- and Mesoporous UiO-Type Metal-Organic Framework.

Here, we report the design, synthesis, and functional testing of enzyme-powered porous micromotors built from a metal-organic framework (MOF). We began by subjecting a presynthesized microporous UiO-type MOF to ozonolysis, to confer it with mesopores sufficiently large to adsorb and host the enzyme catalase (size: 6-10 nm). We then encapsulated catalase inside the mesopores, observing that they are hosted in those mesopores located at the subsurface of the MOF crystals. In the presence of H2O2 fuel, MOF motors (or MOFtors) exhibit jet-like propulsion enabled by enzymatic generation of oxygen bubbles. Moreover, thanks to their hierarchical pore system, the MOFtors retain sufficient free space for adsorption of additional targeted species, which we validated by testing a MOFtor for removal of rhodamine B during self-propulsion.

Roles of defects and linker exchange in phosphate adsorption on UiO-66 type metal organic frameworks: Influence of phosphate concentration

Recently, UiO-66 type metal organic frameworks (MOFs) have been studied as adsorbents for phosphate removal from wastewater; however, the adsorption mechanism with different concentrations of phosphate, especially the roles of defects and linker exchange, are not entirely clear. In this work, the phosphate adsorption mechanism in HCl-UiO-66 and HCl-NH2-UiO-66 were examined by testing the relationship between the adsorbed phosphate and released linker in the adsorption process. Adsorption kinetics studies (3.0 mM phosphate solution) and adsorption isotherm analyses (0.3–6.0 mM phosphate solution) revealed highly linear relationships (R2 = 0.8949–0.9978) between the adsorbed phosphate and released linker for both adsorbents. Further analysis showed that when the adsorbed phosphate was lower than 0.56 mmol/g for HCl-UiO-66 and 0.51 mmol/g for HCl-NH2-UiO-66, phosphate was preferentially adsorbed on the defect sites in the MOFs with no linker release. However, when the adsorbed phosphate exceeded these levels, the defects were saturated by phosphate and linker exchange became the major adsorption mechanism. Based on density functional theory calculations, the obtained strengths of the linkers (H2BDC: Terephthalic acid; NH2-H2BDC: 2-Aminoterephthalic Acid; NO2-H2BDC: 2-Nitroterephthalic Acid) and phosphate species as Lewis bases fall in the order, PO43- > HPO42- > NH2-BDC2- > BDC2- > H2PO4- > NO2-BDC2- > H3PO4, which clearly evidences why linkers can be exchanged by phosphate. Given the propensity for ligand exchange and the resulting structural destabilization, UiO-66 type MOFs is not suggested as ideal adsorbents for phosphate removal from wastewater with high phosphate concentrations.

Modification of the pore environment in UiO-type metal-organic framework toward boosting the separation of propane/propylene

The separation of propane (C3H8) from propylene (C3H6) to obtain high purity C3H6 as a petrochemical raw material is an important, but challenging process. In the traditional industrial process, the separation mainly relies on energy-intensive cryogenic distillation. One alternative process that is currently becoming more attractive in the separation of C3H6 is adsorptive separation technology. Using porous materials, especially C3H8 selective adsorbents, high purity C3H6 can be directly obtained and thus, significantly simplifies the process. Herein, a series of functionalized ligands were introduced into UiO-type materials to finely regulate the C3H8 separation performance. Single-component adsorption isotherms reveal that BUT-10 has a distinct binding affinity for C3H8 over C3H6 over a wide range of temperature from 298 to 338 K and thus, achieved by far the highest C3H8 capture capacity (105 cm3 g−1 at 0.1 bar and 298 K) reported among the C3H8-selective materials reported to date. A combination of Grand Canonical Monte Carlo and density-function theory simulations demonstrate that the favorable pore environment provided by the multiple host-guest interactions toward C3H8 result in the higher C3H8 binding affinity observed in the separation process. Breakthrough experiments indicate that BUT-10 can selectively separate C3H8 from C3H8/C3H6 (1/1 and 1/15, v/v) mixtures and thus, directly produces high purity C3H6 (>99.99%) under ambient conditions.

Diversity-Oriented Metal Decoration on UiO-Type Metal-Organic Frameworks: an Efficient Approach to Increase CO2 Uptake and Catalytic Conversion to Cyclic Carbonates.

A library of metallo-bipyridine UiO-type metal–organic frameworks (MOFs) has been successfully synthesized by postmetallation of a wide range of metal complexes into bidentate bipyridine moieties. Then, a systematic investigation is devoted to a catalytic evaluation of the resultant MOFs containing a binary Lewis acid function for the synthesis of cyclic carbonates from epoxides and carbon dioxide (CO2). The result indicated that the metal-grafted MOFs exhibit improvement in terms of CO2 uptake capacity and catalytic activity in comparison with their nonmetallated counterparts. The comprehensive investigation provides a valuable insight into the synergetic effects of MOF functionalities including metal node, grafted metal, and its counterion in the cycloaddition reaction. Furthermore, the metal coordination modulation due to its benefits such as being a solvent-free process, nearly full conversion to cyclic carbonates, high selectivity and high CO2 uptake, applying atmospheric CO2 pressure, and excellent stability and easy recyclability of the catalyst demonstrates them as promising candidates for practical utilization of CO2 conversion into value-added chemicals.

Uio-Type Metal-Organic Framework Thin Film with Redox-Active Linkers: Development and Charge Transport Behavior

Designing redox-active metal-organic frameworks (MOFs) that can be synthesized as thin films is a key challenge toward their application in electrocatalysis.1 In addition, highly stable MOFs are often electronically insulating in nature, resulting in poor charge transport to redox-catalysts incorporated within the MOF. To overcome these obstacles, we have developed a novel MOF-based thin film platform, which provides electron transport pathways for molecular electrocatalysis.2 The material was rationally designed utilizing the robust Zr-based UiO/PIZOF topology3 and redox-active naphthalene diimide-based linkers (dcphOH-NDI). In addition, hydroxyl groups were included on the dcphOH-NDI linker to facilitate proton transport through the material. When grown on conducting substrates, this material forms thin films (Zr(dcphOH-NDI)@FTO) that display reversible electrochromic behavior. Importantly, nearly all (97%) of the NDI sites are electrochemically active at applied potential. The method of charge propagation through the film was found to proceed via an electron hopping mechanism that is accompanied by counter ion transport. Finally, the MOF thin films were found to function efficiently in aqueous solutions, adding to their potential usefulness in electrocatalytic applications. The fabrication of a UiO/PIZOF-type MOF thin film with linkers having a well-defined electrochemical response, confers unprecedented versatility to utilize postsynthetic methods to introduce catalytic units into a robust and widely studied framework that is now redox-active. In the future, this will allow for the roles of charge propagation and catalysis to be carried out by separate linkers within the MOF film, enabling the individual optimization of each process. Downes, C. A.; Marinescu, S. C. ChemSusChem, 10, 4374−4392 (2017).Johnson, B. A.; Bhunia, A.; Fei, H.; Cohen, S. M.; Ott, S. J. Am. Chem. Soc., 140, 2985−2994 (2018).Cavka, J. H.; Jakobsen, S.; Olsbye, U.; Guillou, N.; Lamberti, C.; Bordiga, S.; Lillerud, K. P. J. Am. Chem. Soc., 130, 13850−13851 (2008); Schaate, A.; Roy, P.; Preuße, T.; Lohmeier, S. J.; Godt, A.; Behrens, P. Chem. - Eur. J., 17, 9320−9325 (2011). Figure 1

Uio-Type Metal-Organic Framework Thin Film with Redox-Active Linkers: Development and Charge Transport Behavior

Designing redox-active metal-organic frameworks (MOFs) that can be synthesized as thin films is a key challenge towards their application in electrocatalysis.1 In addition, highly stable MOFs are often electronically insulating in nature, resulting in poor charge transport to redox-catalysts within the MOFs. To overcome these obstacles, we have developed a novel MOF-based thin film platform, which provides electron transport pathways for molecular electrocatalysis.2 The material was rationally designed utilizing the robust Zr-based UiO/PIZOF topology3 and redox-active naphthalene diimide-based linkers (dcphOH-NDI). In addition, hydroxyl groups were included on the dcphOH-NDI linker to facilitate proton transport through the material. When grown on conducting substrates (fluorine-doped tin oxide, FTO), this material forms thin films (Zr(dcphOH-NDI)@FTO) that display reversible electrochromic behavior. Importantly, nearly all (97%) of the NDI sites are electrochemically active at applied potential. The method of charge propagation through the film was found to proceed via an electron hopping mechanism that is accompanied by counter ion transport. Finally, the MOF thin films were found to function efficiently in aqueous solutions, adding to their potential usefulness in electrocatalytic applications. The fabrication of a UiO/PIZOF-type MOF thin film with linkers having a well-defined electrochemical response, confers unprecedented versatility to utilize postsynthetic methods to introduce catalytic units into a robust and widely studied framework that is now redox-active. In the future, this will allow for the roles of charge propagation and catalysis to be carried out by separate linkers within the MOF film, enabling the individual optimization of each process. Downes, C. A.; Marinescu, S. C. ChemSusChem, 10, 4374−4392 (2017).Johnson, B. A.; Bhunia, A.; Fei, H.; Cohen, S. M.; Ott, S. J. Am. Chem. Soc., 140, 2985−2994 (2018).Cavka, J. H.; Jakobsen, S.; Olsbye, U.; Guillou, N.; Lamberti, C.; Bordiga, S.; Lillerud, K. P. J. Am. Chem. Soc., 130, 13850−13851 (2008); Schaate, A.; Roy, P.; Preuße, T.; Lohmeier, S. J.; Godt, A.; Behrens, P. Chem. - Eur. J., 17, 9320−9325 (2011).