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1.
Adv Mater ; : e2004414, 2020 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-32902012

RESUMO

Metal-organic frameworks (MOFs) based on group 3 and 4 metals are considered as the most promising MOFs for varying practical applications including water adsorption, carbon conversion, and biomedical applications. The relatively strong coordination bonds and versatile coordination modes within these MOFs endow the framework with high chemical stability, diverse structures and topologies, and interesting properties and functions. Herein, the significant progress made on this series of MOFs since 2018 is summarized and an update on the current status and future trends on the structural design of robust MOFs with high connectivity is provided. Cluster chemistry involving Y, lanthanides (Ln, from La to Lu), actinides (An, from Ac to Lr), Ti, and Zr is initially introduced. This is followed by a review of recently developed MOFs based on group 3 and 4 metals with their structures discussed based on the types of inorganic or organic building blocks. The novel properties and arising applications of these MOFs in catalysis, adsorption and separation, delivery, and sensing are highlighted. Overall, this review is expected to provide a timely summary on MOFs based on group 3 and 4 metals, which shall guide the future discovery and development of stable and functional MOFs for practical applications.

2.
J Am Chem Soc ; 2020 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-32876449

RESUMO

Combining synthesis, infrared spectroscopy, and ab initio modeling we show that the titanium-based porous framework Ti-MOF-74 has potential as an environmental nitric oxide (NO) scavenger, exhibiting an extraordinarily strong binding affinity and selectivity over other flue-gas components. The robustness upon exposure to water vapor and high flue-gas stack temperatures suggests that this material can perform well in an industrial environment. In-depth analysis of the Ti-NO bond indicates that the NO forms a strong covalent bond with the Ti. The process of this NO bond formation involves a reaction with the OH- capping groups of the Ti to form NOx groups, after which the excess NO binds to the open Ti metal sites. Ti-MOF-74 thus becomes, to the best of our knowledge, the first known porous framework that binds NO significantly stronger than water, providing novel avenues for environmental and physiological scavenging applications.

3.
Inorg Chem ; 2020 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-32856902

RESUMO

Metal-organic frameworks (MOFs) have been explored as crystal sponges (CSs) to organic substrates, but attention had rarely been paid to inorganic substrates. Herein, hierarchical zirconium-based MOFs exhibiting different topological structures had been fabricated by modulating the functional groups of the V-shaped linkers, including a new 4-fold-interpenetrating one, which displays a great performance as a CS applicable to inorganic matter (I2 and ReO4-) even in the extreme conditions.

4.
J Am Chem Soc ; 2020 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-32786758

RESUMO

The oxygen reduction reaction (ORR) is central in carbon-neutral energy devices. While platinum group materials have shown high activities for ORR, their practical uses are hampered by concerns over deactivation, slow kinetics, exorbitant cost, and scarce nature reserve. The low cost yet high tunability of metal-organic frameworks (MOFs) provide a unique platform for tailoring their characteristic properties as new electrocatalysts. Herein, we report a new concept of design and present stable Zr-chain-based MOFs as efficient electrocatalysts for ORR. The strategy is based on using Zr-chains to promote high chemical and redox stability and, more importantly, tailor the immobilization and packing of redox active-sites at a density that is ideal to improve the reaction kinetics. The obtained new electrocatalyst, PCN-226, thereby shows high ORR activity. We further demonstrate PCN-226 as a promising electrode material for practical applications in rechargeable Zn-air batteries, with a high peak power density of 133 mW cm-2. Being one of the very few electrocatalytic MOFs for ORR, this work provides a new concept by designing chain-based structures to enrich the diversity of efficient electrocatalysts and MOFs.

5.
J Am Chem Soc ; 142(35): 15020-15026, 2020 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-32786762

RESUMO

The pore engineering of microporous metal-organic frameworks (MOFs) has been extensively investigated in the past two decades, and an expansive library of functional groups has been introduced into various frameworks. However, the reliable procurement of MOFs possessing both a targeted pore size and preferred functionality together is less common. This is especially important since the applicability of many elaborately designed materials is often restricted by the small pore sizes of microporous frameworks. Herein, we designed and synthesized a mesoporous MOF based on Zr6 clusters and tetratopic carboxylate ligands, termed PCN-808. The accessible coordinatively unsaturated metal sites as well as the intrinsic flexibility of the framework make PCN-808 a prime scaffold for postsynthetic modification via linker installation. A linear ruthenium-based metalloligand was successfully and precisely installed into the walls of open channels in PCN-808 while maintaining the mesoporosity of the framework. The photocatalytic activity of the obtained material, PCN-808-BDBR, was examined in the aza-Henry reaction and demonstrated high conversion yields after six catalytic cycles. Furthermore, thanks to the mesoporous nature of the framework, PCN-808-BDBR also exhibits exceptional yields for the photocatalytic oxidation of dihydroartemisinic acid to artemisinin.

6.
J Am Chem Soc ; 2020 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-32657127

RESUMO

The application scope of metal-organic frameworks (MOFs) is severely restricted by their weak chemical stability and limited pore size. A robust MOF with large mesopores is highly desired, yet poses a great synthetic challenge. Herein, two chemically stable Ni(II)-pyrazolate MOFs, BUT-32 and -33, were constructed from a conformation-matched elongated pyrazolate ligand through the isoreticular expansion. The two MOFs share the same sodalite-type net, but have different pore sizes due to the network interpenetration in BUT-32. Controlled syntheses of the two MOFs have been achieved through precisely tuning reaction conditions, where the microporous BUT-32 was demonstrated to be a thermodynamically stable product while the mesoporous BUT-33 is kinetically favored. To date, BUT-32 represents the first example of Ni4-pyrazolate MOF whose structure was unambiguously determined by single-crystal X-ray diffraction. Interestingly, the kinetic product BUT-33 integrates 2.6 nm large mesopores with accessible Ni(II) active sites and remarkable chemical stability even in 4 M NaOH aqueous solution and 1 M Grignard reagent. This MOF thus demonstrated an excellent catalytic performance in carbon-carbon coupling reactions, superior to other Ni(II)-MOFs including BUT-32. These findings highlight the importance of kinetic control in the reticular synthesis of mesoporous MOFs, as well as their superiority in heterogeneous catalysis.

7.
Chem Commun (Camb) ; 56(63): 9016-9019, 2020 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-32638737

RESUMO

A chiral metal-organic framework possessing an open amphiphilic channel is constructed from a dicarboxylate ligand derived from an amino acid and is shown to be an efficient and recyclable chiral solid adsorbent, which is capable of separating racemic secondary alcohols, epoxides, and ibuprofen with very high enantioselectivity.

8.
Artigo em Inglês | MEDLINE | ID: mdl-32613736

RESUMO

Intriguing properties and functions are expected to implant into metal-organic layers (MOLs) to achieve tailored pore environments and multiple functionalities owing to the synergies among multiple components. Herein, we demonstrate a facile one-pot synthetic strategy to incorporate multiple functionalities into stable zirconium MOLs via secondary ligand pillaring. Through the combination of Zr6 -BTB (BTB=benzene-1,3,5-tribenzoate) layers and diverse secondary ligands (including ditopic and tetratopic linkers), 31 MOFs with multi-functionalities were systematically prepared. Notably, a metal-phthalocyanine fragment was successfully incorporated into this Zr-MOL system, giving rise to an ideal platform for the selective oxidation of anthracene. The organic functionalization of two-dimensional MOLs can generate tunable porous structures and environments, which may facilitate the excellent catalytic performance of as-synthesized materials.

9.
J Phys Chem Lett ; 2020 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-32496774

RESUMO

According to the solid-state 13C, 31P NMR study and 13C CSA measurements, aromatic rings in the layered metal(IV) phosphonate materials behavior as low-energy rotors at rotation activation energy Eact of 1.4 - 3.0 kcal/mol. The rotational mechanism consists of 1800 - flips and librations around C(1)-C(4) axis. The amplitude of the librations, added to the flips, grows with the temperature shifting the reorientations towards rotational diffusion at high temperatures.

10.
J Am Chem Soc ; 2020 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-32564596

RESUMO

The recombination of electron-hole pairs severely detracts from the efficiency of photocatalysts. This issue could be addressed in metal-organic frameworks (MOFs) through optimization of the charge-transfer kinetics via rational design of structures at atomic level. Herein, a pyrazolyl porphyrinic Ni-MOF (PCN-601), integrating light harvesters, active catalytic sites, and high surface areas, has been demonstrated as a superior and durable photocatalyst for visible-light-driven overall CO2 reduction with H2O vapor at room temperature. Kinetic studies reveal that the robust coordination spheres of pyrazolyl groups and Ni-oxo clusters endow PCN-601 with proper energy band alignment and ultrafast ligand-to-node electron transfer. Consequently, the CO2-to-CH4 production rate of PCN-601 far exceeds those of the analogous MOFs based on carboxylate porphyrin and the classic Pt/CdS photocatalyst by more than 3- and 20-fold, respectively. The reaction avoids the use of hole scavengers and proceeds in a gaseous phase which can take full advantage of the high gas uptake of MOFs. This work demonstrates that the rational design of coordination spheres in MOF structures not only reconciles the contradiction between reactivity and stability but also greatly promotes the interfacial charge transfer to achieve optimized kinetics, providing guidance for the design of highly efficient MOF photocatalysts.

11.
Artigo em Inglês | MEDLINE | ID: mdl-32543765

RESUMO

Modification of the external surfaces of metal-organic frameworks offers a new level of control over their adsorption behavior. It was previously shown that capping of MOFs with ethylenediamine (EDA) can effectively retain small gaseous molecules at room temperature. Reported here is a temperature-induced variation in the capping-layer gate-opening mechanism through a combination of in situ infared experiments and ab initio simulations of the capping layer. An atypical acceleration and increase in the loading of weakly adsorbed molecules upon raising the temperature above room temperature is observed. These findings show the discovery of novel temperature-dependent kinetics that goes beyond standard kinetics and suggest a new avenue for tailoring selective adsorption by thermally tuning the surface barrier.

12.
Artigo em Inglês | MEDLINE | ID: mdl-32406228

RESUMO

Polycyclic aromatic hydrocarbons such as perylene and pyrene and their derivatives are highly emissive fluorophores in solution. However, the practical applications of these materials in the field of molecular electronic and light-emitting devices are often hindered by self-quenching effects because of the formation of nonfluorescent aggregates in concentrated solutions or in the solid state. Herein, we demonstrate that aggregation-caused quenching of perylenes can be minimalized by molecular incorporation into metal-organic frameworks (MOFs). This study utilized a stable Zr6 cluster-based MOF, UiO-67, as a matrix. Linear linkers containing photoresponsive moieties were designed and incorporated into the parent UiO-67 scaffold through the partial replacement of the nonfluorescent linkers of a similar length, forming mixed-linker MOFs. The average distance between perylene moieties was tuned by changing the linker ratios, thus controlling the fluorescence intensity, emission wavelength, and quantum yield. Molecular modeling was further adopted to correlate the number of isolated perylene linkers within the framework with the ratio between the two linkers, thereby rationalizing the change in the observed fluorescent properties. Taking advantage of the tunable fluorescence, inherent porosity, and high chemical stability of this MOF platform, it was applied as a fluorescent sensor for oxygen detection in the gas phase, a model reaction, showing fast response and good recyclability.

13.
ACS Nano ; 2020 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-32330000

RESUMO

Atomically dispersed metal and nitrogen co-doped carbon (M-N/C) catalysts hold great promise for electrochemical CO2 conversion. However, there is a lack of cost-effective synthesis approaches to meet the goal of economic mass production of single-atom M-N/C with desirable carbon support architecture for efficient CO2 reduction. Herein, we report facile transformation of commercial carbon nanotube (CNT) into isolated Fe-N4 sites anchored on carbon nanotube and graphene nanoribbon (GNR) networks (Fe-N/CNT@GNR). The oxidization-induced partial unzipping of CNT results in the generation of GNR nanolayers attached to the remaining fibrous CNT frameworks, which reticulates a hierarchically mesoporous complex and thus enables a high electrochemical active surface area and smooth mass transport. The Fe residues originating from CNT growth seeds serve as Fe sources to form isolated Fe-N4 moieties located at the CNT and GNR basal plane and edges with high intrinsic capability of activating CO2 and suppressing hydrogen evolution. The Fe-N/CNT@GNR delivers a stable CO Faradaic efficiency of 96% with a partial current density of 22.6 mA cm-2 at a low overpotential of 650 mV, making it one of the most active M-N/C catalysts reported. This work presents an effective strategy to fabricate advanced atomistic catalysts and highlights the key roles of support architecture in single-atom electrocatalysis.

14.
Artigo em Inglês | MEDLINE | ID: mdl-32243687

RESUMO

Hierarchically porous metal-organic frameworks (HP-MOFs) facilitate mass transfer due to mesoporosity while preserving the advantage of microporosity. This unique feature endows HP-MOFs with remarkable application potential in multiple fields. Recently, new methods such as linker labilization for the construction of HP-MOFs have emerged. To further enrich the synthetic toolkit of MOFs, we report a controlled photolytic removal of linkers to create mesopores within microporous MOFs at tens of milliseconds. Ultraviolet (UV) laser has been applied to eliminate "photolabile" linkers without affecting the overall crystallinity and integrity of the original framework. Presumably, the creation of mesopores can be attributed to the missing-cluster defects, which can be tuned through varying the time of laser exposure and ratio of photolabile/robust linkers. Upon laser exposure, MOF crystals shrank while metal oxide nanoparticles formed giving rise to the HP-MOFs. In addition, photolysis can also be utilized for the fabrication of complicated patterns with high precision, paving the way towards MOF lithography, which has enormous potential in sensing and catalysis.

15.
Angew Chem Int Ed Engl ; 59(24): 9319-9323, 2020 06 08.
Artigo em Inglês | MEDLINE | ID: mdl-32174003

RESUMO

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).

16.
Chemistry ; 2020 Mar 03.
Artigo em Inglês | MEDLINE | ID: mdl-32128881

RESUMO

Nanosized α-zirconium phenylphosphonate particles were successfully prepared by the reaction between different zirconium sources and molten phenylphosphonic acid in the absence of solvent. The resultant nanoplates exhibit particle sizes in the range of 15 to 30 nm. The use of a topotactic anion exchange method starting from α-zirconium phosphate instead resulted in the generation of 15 to 180 nm plates, while also resulting in nanoparticles with a higher degree of crystallinity. The topotactic anion exchange of the phosphate groups by phenylphosphonate groups could be performed to completion when performed in molten phenylphosphonic acid. Characterization of both the final products as well as the individual steps in the anion exchange were performed by powder XRD, fast neutron activation analysis, TGA, FTIR spectroscopy, TEM, solid-state NMR and XPS.

17.
J Am Chem Soc ; 2020 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-32188245

RESUMO

Adsorptive separation of acetylene (C2H2) from carbon dioxide (CO2) promises a practical way to produce high-purity C2H2 required for industrial applications. However, challenges exist in the pore environment engineering of porous materials to recognize two molecules due to their similar molecular sizes and physical properties. Herein, we report a strategy to optimize pore environments of multivariate metal-organic frameworks (MOFs) for efficient C2H2/CO2 separation by tuning metal components, functionalized linkers, and terminal ligands. The optimized material UPC-200(Al)-F-BIM, constructed from Al3+ clusters, fluorine-functionalized organic linkers, and benzimidazole terminal ligands, demonstrated the highest separation efficiency (C2H2/CO2 uptake ratio of 2.6) and highest C2H2 productivity among UPC-200 systems. Experimental and computational studies revealed the contribution of small pore size and polar functional groups on the C2H2/CO2 selectivity and indicated the practical C2H2/CO2 separation of UPC-200(Al)-F-BIM.

18.
Artigo em Inglês | MEDLINE | ID: mdl-32011112

RESUMO

The removal of toxic organic compounds (TOCs) using highly porous solids such as metal-organic frameworks (MOFs) has gained significant attention over the past decade. In this study, it has been demonstrated that the efficiency of PCN-250 as a heterogeneous catalyst porous coordination network (PCN) for both Fenton and photo-Fenton reactions can be improved by the isomorphic substitution of Mn and Co for Fe, while it can be inhibited by the substitution of Ni for Fe. Furthermore, the Mn-substituted sample named PCN-250(Fe2Mn) decomposed 100% of methylene blue (MB) in solution in 300 min and displayed good recyclability over three cycles. This work establishes that the highly porous, commercially available, and robust family of MOFs named PCN-250 has the potential to be used as catalysts for Fenton and photo-Fenton reactions as well as broader advanced oxidation processes (AOP) for water purification applications. Overall, this work successfully demonstrates not only the ability to perform isomorphic substitution of various metals within MOFs but also the effect of the substitution on the resulting catalytic performance.

19.
J Am Chem Soc ; 142(10): 4732-4738, 2020 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-32058715

RESUMO

The continuous variation of the lattice metric in metal-organic frameworks (MOFs) allows precise control over their chemical and physical properties. This has been realized herein by a series of mixed-linker and Zr6-cluster-based MOFs, namely, continuously variable MOFs (CVMOFs). Similar to the substitutional solid solutions, organic linkers with different lengths and various ratios were homogeneously incorporated into a framework rather than being allowed to form separate phases or domains, which was manifested by single-crystal X-ray diffraction, powder X-ray diffraction, fluorescence quenching experiments, and molecular simulations. The unit cell dimension, surface area, and pore size of CVMOFs were precisely controlled by adopting different linker sets and linker ratios. We demonstrate that CVMOFs allow the continuous and fine tailoring of cell-edge lengths from 17.83 to 32.63 Å, Brunauer-Emmett-Teller (BET) surface areas from 585 to 3791 m2g-1, and pore sizes up to 15.9 Å. Furthermore, this synthetic strategy can be applied to other MOF systems with various metal nodes thus allowing for a variety of CVMOFs with unprecedented tunability.

20.
Chem Commun (Camb) ; 2020 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-32110788

RESUMO

Isotropic and anisotropic motions and molecular states of pyridine-d5, adsorbed on the surface within the pores of a layered Sn(iv) phosphonate-phosphate material (1) have been characterized thermodynamically and kinetically by solid-state NMR. The data obtained provide formulation of macrostructure and shapes of pores in 1.

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