Effective Dual-Functional Metal-Organic Framework (DF-MOF) as a Catalyst for the Solvent-Free Cycloaddition Reaction.

A new porous metal-organic framework, [Co (oba) (bpdh)]·(DMF) (TMU-63), containing accessible nitrogen-rich diazahexadiene groups was successfully prepared with the solvothermal assembly of 5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene (4-bpdh), 4,4'-oxybis(benzoic) acid (oba), and Co(II) ions. The combination of Lewis basic functional groups and porosity leads to high performance in CO2 adsorption and conversion in the cycloaddition reaction of epoxides under solvent-free conditions. To further enhance the catalytic efficiency of TMU-63, we introduced a highly acidic malonamide ligand into the structure via solvent-assisted ligand exchange (SALE) as a postsynthesis method. Incorporating different percentages of N1,N3-di(pyridine-4-yl) malonamide linker (4-dpm) into TMU-63 created a new porous structure. Powder X-ray diffraction (PXRD) and NMR spectroscopy confirmed that 4-bpdh was successfully replaced with 4-dpm in the daughter MOF, TMU-63S. The catalytic activity of both MOFs was confirmed by significant amounts of CO2 cycloaddition of epoxides under solvent-free conditions. The catalytic cycloaddition activities were found to be well-correlated with the Lewis base/Brønsted acid distributions of the materials examined in the TMU-63S series, showing that the concurrent presence of both acid and base sites was desirable for high catalytic activity. Furthermore, the heterogeneous catalysts could easily be separated out from the reaction mixtures and reused four times without loss of catalytic activity and with no structural deterioration.

Ultrasound Irradiation Assisted Synthesis of Luminescent Nano Amide-Functionalized Metal-Organic Frameworks; Application Toward Phenol Derivatives Sensing.

Two nano amide-functionalized metal-organic frameworks (MOFs) with molecular formula [Co(oba) (bpta)]·(DMF)2 TMU-50 and [Co2(oba)2 (bpfn)]·(DMF)2.5 TMU-51 obtained under ultrasonic method without any surfactants. The only difference between the two selected amide functionalized pillar ligands, N,N'-bis(4-pyridinyl)-terephthalamide (bpta), and N,N'-bis-(4-pyridylformamide)-1,5-naphthalenediamine (bpfn), is related to the naphthyl group, which led to the different luminescence properties of the nano frameworks. In this study, the special ability of the luminescent nano MOFs were investigated to sensitize nitroaromatic compounds. Due to its unique and porous framework, Nano TMU-50 shows a good sensitivity towards nitro phenol by strong fluorescence emission with a detection limit of 2 × 10-3 mM-1. Both nano MOF structures were characterized via many analyses such as powder X-ray diffraction, Field Emission Scanning Electron Microscopy (FE-SEM), elemental analysis, and FTIR spectroscopy. Moreover, the effect of a number of important parameters including initial reagent concentrations, power of ultrasound, time on morphology, and size of nano structures were examined. According to the fluorescence titration results, the activated nano-TMU-50 detected NP selectively with a quick response.

Rational morphology control of nano-scale amide decorated metal-organic frameworks by ultrasonic method: Capability to selective and sensitive detection of nitro explosives.

One of the key challenges in rational design and synthesis of metal-organic frameworks (MOFs) is defined control over size and morphology for using these materials in many more advanced applications. Combining ultrasonic method and capping groups makes it possible to control the size and change the morphology of metal organic frameworks without changing material compositions. Nano TMU-46, 47 and 48 with copper metal center and amide functionalized pillar were synthesized by using ultrasonic irritation and characterized by FE-SEM, powder X-ray diffraction, elemental analysis, and FTIR spectroscopy. Sensing properties of these nano scale materials and the correlation between the nano structure and nitroaromatic compounds detection were studied. Nano TMU-46 due to its special and porous structure and available functional group show strong luminescence emission, which is selectively sensitive to Trinitrophenol (TNP) with a detection limit of 10-3 M. Furthermore, multiple morphological transition in the structure of these crystals were observed with using different modulators. This morphology transition, in fact, successfully led to significant change in sensing properties of this structure and decreased the detection limit to 10-5 M.

Coordinatively unsaturated metal sites (open metal sites) in metal-organic frameworks: design and applications.

Metal-organic frameworks (MOFs) can contain open metal sites (OMS) or coordinatively unsaturated sites (CUS) or open coordination sites (OCS) when vacant Lewis acid sites on the metal ions or cluster nodes have been generated. This review combines for the first time all aspects of OMS in MOFs, starting from different preparation strategies over theoretical studies on the effects of OMS with host-guest interactions up to distinct OMS-MOF applications. In the experimental part the focus of this review is on MOFs with proven OMS formation which are not only invoked but are clearly verified by analytical methods.

The targeted design of dual-functional metal-organic frameworks (DF-MOFs) as highly efficient adsorbents for Hg2+ ions: synthesis for purpose.

Designing adsorbents with accessible chelating sites and achieving high contaminant purification efficiency are still important to overcome environmental remediation challenges. As one of the significant global concerns, the presence of heavy metal ions in the environment has attracted increasing attention due to their toxicity, carcinogenicity, and bioaccumulation in the food chain. Herein, we performed a targeted design of a new dual-functionalized metal-organic framework (DF-MOF) by incorporating different percentages of the N1,N3-di(pyridine-4-yl) malonamide ligand (S) into urea-containing MOF (TMU-32); the produced material was labeled as TMU-32S (with 33%, 65%, and 100% incorporation percentages). Designing DF-MOF is our "design-for-purpose" approach for the decoration of MOF walls by suitable functional groups, resulting in high removal capacity of heavy metal ions. Among the TMU-32S series having different concentrations of the S ligand, TMU-32S-65% demonstrated exceptional Hg2+ ion selectively. To the best of our knowledge, this is the first report of mixed urea-malonamide-based MOF, which provides a proper coordination site to strongly coordinate with Hg2+ ions, along with 1428 mg g-1 maximum adsorption capacity. Generally, we attributed the impressive implementation of TMU-32S-65% to the synergistic effects of both hydrophilic chelating urea and the malonamide functional group. Hence, the results reported in this work indicate the exceptional potential of DF-MOFs for the high accomplishment of environmental remediation.

Solvent-assisted ligand exchange (SALE) for the enhancement of epoxide ring-opening reaction catalysis based on three amide-functionalized metal-organic frameworks.

In recent years, functionalized pillar ligands have gained significant interests due to their important role in MOF structure and performance. The synthesis of MOF compounds with a particular functionalized ligand is not always successful, and sometimes, synthesis cannot be achieved easily or directly, even by employing several methods. However, this limitation can be overcome by applying a post-synthesis step that swaps the functional groups without changing the backbone of the pillar ligand. Solvent-assisted ligand exchange (SALE) is a post-synthesis method that has been used for confronting this challenge by replacing a functional group with an alternative. Through this investigation, we tried to improve the properties of MOF compounds and increase their catalytic efficiency by importing new functional groups into their structures. The N1,N3-di (pyridine-4-yl) malonamide linker (S) is a pillar ligand, which does not easily enter into the structure during the synthesis of MOF compounds. Therefore, to solve this issue, amide-functionalized, benzene-core ligand derivatives were designed as linkers to manufacture the new 3D structures [Co(oba)(bpta)]·(DMF)2 TMU-50 and [Co2(oba)2(bpfn)]·(DMF)2.5 TMU-51 and the novel 2D structure [Co(oba)(bpfb)]·(DMF)2 TMU-49. These structures were achieved by layering the compounds via hydrothermal reaction. Moreover, the ability of these structures to act as catalysts was evaluated using the methanolysis reaction of epoxides. To increase the MOF catalytic efficiency, we designed the N1,N3-di (pyridine-4-yl) malonamide linker (S) as a malonamide pillar ligand, which contains an acidic hydrogen that is suitable for catalyzing an epoxide ring-opening reaction and therefore enhancing the catalytic activity. As the synthesis of the MOF structure with this linker was not successful, we designed three new structures by incorporating different percentages of S linkers by exchanging the acylamide functional group with malonamide via the SALE pathway. The acylamide functional group was successfully replaced and produced daughter MOFs TMU-49S, TMU-50S and TMU-51S. PXRD and NMR spectroscopy confirmed that the S linker was incorporated into the acylamide-MOF structure. The obtained materials TMU-49S, TMU-50S and TMU-51S are isostructural with their parent frameworks. The S spacer significantly improved the catalytic properties of the MOF compounds in the ring-opening reaction of epoxides, with TMU-50S showing a 98% catalytic efficiency after incorporating the S linker. The catalysts could be recycled without any significant loss in the catalytic efficiency.

Ultrasound assisted synthesis of amide functionalized metal-organic framework for nitroaromatic sensing.

Nano plates of zinc(II) based metal-organic framework (MOF) were prepared via ultrasonic method without any surfactants at room temperature and atmospheric pressure. Control of particle size and morphology was enhanced in this synthesis method. Nano plates of an interpenetrated amide-functionalized metal-organic framework, [Zn2(oba)2(bpfb)]·(DMF)5, TMU-23, (H2oba = 4,4'-oxybis(benzoic acid); bpfb = N,N'-bis-(4-pyridylformamide)-1,4-benzenediamine, DMF = N,N-dimethyl formamide), was synthesized under ultrasound irradiation in different concentrations of initial precursor. The nano structure and morphology of the synthesized MOF were characterized by Field Emission Scanning Electron Microscopy (FE-SEM), powder X-ray diffraction, thermo gravimetric analysis (TGA), elemental analysis and FTIR spectroscopy. Moreover, Fluorescence emissions of nanoplates have been studied. Amide-functionalized MOF shows high selectivity for sensing of nitroaromatic compounds such as nitrophenol, nitroaniline, and nitrobenzene in acetonitrile solution. Fluorescence intensity decreased with increasing contents of nitroaromatics in acetonitrile solution due to fluorescence quenching effect.