A facile method to introduce iron secondary metal centers into metal–organic frameworks
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Linker
Characterization
Iron pentacarbonyl
Metal–organic frameworks (MOFs) are nanoporous materials composed of organic linkers and inorganic nodes. The large variety of linkers and nodes and the multiple ways to combine them make MOFs highly tunable materials, which are thoroughly studied for their use in, e.g., catalysis, gas capture, and separation. The chemistry of MOFs is further enriched by defects, e.g., missing linker defects, which provide active sites for catalysis or anchoring sites for introducing new functionalities. A commonly reported method to quantify linker defects assumes the presence of one type of linker and the complete removal of capping agents, solvents, and other impurities upon activation at high temperature, e.g., 400 °C (M-400). However, attempts to use this method for MOFs containing different types of linkers, also called multivariate MOFs (MTV-MOFs), or capping agents that are not completely removed at 400 °C, give inaccurate results and hamper comparing results from different publications. In this work, we have developed a new procedure to compute missing linker defects in Zr-based MOFs using standard analytical techniques to quantify the capping agents that remain in the MOF upon activation at 200 °C (M-200). This method, which has been tested in UiO-66/67 based MOFs, should be applicable to any MOF that (1) has known decomposition products, (2) has no missing cluster defects, (3) has empty pores or contain species that can be quantified after activation, and (4) has a known node composition at 200 °C.
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We report a topology-guided, precise insertion of three distinct secondary linkers into a zirconium-based metal–organic framework, NPF-300. Constructed from a tetratopic linker L and Zr6 cluster, NPP-300 exhibits a unique scu topology and certain flexibility along the crystallographic a axis, and in conjunction with the conformation change of the primary ligand, is able to accommodate the stepwise insertion of three different secondary linkers along the a and c axes. Size-matching and mechanic strain of the resulting framework are two important factors that determine the chemical stability of the inserted linkers. Secondary linker insertion in NPF-300 significantly enables not only its porosity but also potentials to install up to three different functional groups for the construction of multivariate MOFs with homogeneity.
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In this work, we introduce a novel enantiopure chiral spiro bistriazolate linker molecule (H 2-bibta ) and the corresponding first enantiopure bistriazolate-based metal–organic framework, CFA-18 (Coordination Framework Augsburg-18 ).
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Metal-organic framework MOF-5 (i.e. IRMOF-1) with the chemical structure of Zn4O(BDC)3 were successfully synthesized using room temperature synthesis approach of direct-mixing method ans liquid-crystal templating method. The metal clusters organic linker used was benzenedicarboxylic acid (BDC). Direct-mixing approach resulted in MOF-5 with tetragonal cell while the liquid-crystal templating method resulted in cubic structure. The metal/linker ratios were varied from 0.1 to 1 to study the effect of metal linker on the formation of MOF-5 materials and their characteristics. The crystallinity of the evacuated framework MOF-5 materials were increased when the metal/organic linker ratios were increased from 0.3 to 0.5. However, the cubic structure of the evacuated framework was relatively disrupted at metal/linker ratio 0.7.
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Abstract In a previous study, a novel cellobiohydrolase, PoCel6A, with new enzymatic activity against p ‐nitrophenyl‐β‐ D ‐cellobioside ( p NPC), was purified from Penicillium oxalicum. The cellulose‐binding module and catalytic domain of PoCel6A showed a high degree of sequence similarity with other fungal Cel6As. However, PoCel6A had 11 more amino acids in the linker region than other Cel6As. To evaluate the relationship between the longer linker of PoCel6A and its enzymatic activity, 11 amino acids were deleted from the linker region of PoCel6A. The shortened PoCel6A linker nullified the enzymatic activity against p NPC but dramatically increased the enzyme's capacity for crystalline cellulose degradation. The shortened linker segment appeared to have no effect on the secondary structural conformation of PoCel6A. Another variant (PoCel6A‐6pro) with six consecutive proline residues in the interdomain linker had a higher rigid linker, and no enzymatic activity was observed against soluble and insoluble substrate. The flexibility of the linker had an important function in the formation of active cellulase. The length and flexibility of the linker is clearly able to modify the function of PoCel6A and induce new characteristics of Cel6A.
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Cholestane
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A series of metal–organic frameworks (MOFs) (PCN-606-OH-TPDC, PCN-606-OMe-TPDC, PCN-606-OH-EDDB, and PCN-606-OMe-EDDB) are synthesized through linker installation onto open sites of 8-connected Zr6 clusters in PCN-606-R (where R = −OH or −OMe) parent frameworks of differing flexibilities. The two postsynthetically installed linear linkers possess slight differences in length and bulk, which result in a noticeable difference in the installation temperatures, reflective of a different thermodynamic barrier to incorporation into PCN-606-R. The X-ray crystallographic data as well as the N2 adsorption properties of these four newly produced MOFs are explored and compared to gain a more comprehensive understanding of the implications that this difference in linker size and bulk have during insertion into flexible MOFs.
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Iron-coated Nd-Fe-B composite powder was prepared by thermal decomposition of iron pentacarbonyl in an inert organic solvent in the presence of alkylamine. Though this method is based on a modified solution-phase process to synthesize highly size-controlled iron nanoparticles, it is in turn featured by a suppressed formation of iron nanoparticles to achieve an efficient iron coating solely onto the surfaces of rare-earth magnet powder. The Nd-Fe-B magnetic powder was successfully coated by iron shells whose thicknesses were of the order of submicrometer to micrometer, being tuneable by the amount of initially loaded iron pentacarbonyl in a reaction flask. The amount of the coated iron reached to more than 10 wt.% of the initial Nd-Fe-B magnetic powder, which is practically sufficient to fabricate Nd-Fe-B/α-Fe nanocomposite permanent magnets.
Iron pentacarbonyl
Inert gas
Iron powder
Carbonyl iron
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Superparamagnetism
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Fusion protein was a genetic expression product, which was composed by two or more head-to-tail ligation genic coding region that were controlled by the same regulatory sequence. The design of linker played an important part in the fusion protein with connecting peptide. Linker designing, linker construction, linker classify, the function of linker, the problem arised and solved in the fusion protein with linker, were reviewed in this article.
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