Crystal engineering of the nbo metal–organic framework (MOF) platform MOF‐505 with a custom‐designed azamacrocycle ligand (1,4,7,10‐tetrazazcyclododecane‐N,N′,N′′,N′′′‐tetra‐p‐methylbenzoic acid) leads to a high density of well‐oriented Lewis active sites within the cuboctahedral cage in MMCF‐2, [Cu2(Cu‐tactmb)(H2O)3(NO3)2]. This MOF demonstrates high catalytic activity for the chemical fixation of CO2 into cyclic carbonates at room temperature under 1 atm pressure.
A majority of metal–organic frameworks (MOFs) fail to preserve their physical and chemical properties after exposure to acidic, neutral, or alkaline aqueous solutions, therefore limiting their practical applications in many areas. The strategy demonstrated herein is the design and synthesis of an organic ligand that behaves as a buffer to drastically boost the aqueous stability of a porous MOF (JUC‐1000), which maintains its structural integrity at low and high pH values. The local buffer environment resulting from the weak acid–base pairs of the custom‐designed organic ligand also greatly facilitates the performance of JUC‐1000 in the chemical fixation of carbon dioxide under ambient conditions, outperforming a series of benchmark catalysts.
Das 12‐fach verknüpfte Metall‐organische Gerüst (MOF) MMPF‐3 wurde ausgehend von einem Cobalt(II)‐Porphyrin erzeugt und enthält dieselben polyedrischen supramolekularen Bausteine wie das prototypische fcu‐MOF‐1. Die Nanohohlräume von MMPF‐3 verfügen jeweils über achtzehn katalytisch aktive Cobaltzentren, und die hohe Dichte von ca. fünf Cobaltzentren pro nm3 sorgt dafür, dass MMPF‐3 anderen MOFs in der katalytischen Epoxidierung von trans‐Stilben überlegen ist.
The Cover Feature shows how, serving as an artificial photosynthesis system, the rationally designed Ti/Zr porphyrinic metal–organic framework demonstrates gas‐phase water oxidation‐assisted selective photoreduction of CO2 under visible‐light irradiation. More information can be found in the Communication by W.‐Y. Gao, H. T. Ngo, et al.
Inspiration for molecular design and construction can be derived from mathematically based structures.I nt he quest for new materials,the adaptation of new building blocks can lead to unexpected results.T owards these ends,t he quantitative single-step self-assembly of as hape-persistent, Archimedean-based building block, which generates the largest molecular sphere (a cuboctahedron) that has been unequivocally characterized by synchrotron X-ray analysis,i sd escribed. The unique properties of this new construct give rise to ad ilution-based transformation into two identical spheres (octahedra) each possessing one half of the molecular weight of the parent structure;c oncentration of this octahedron reconstitutes the original cuboctahedron. These chemical phenomena are reminiscent of biological fission and fusion processes.The large 6nmc age structure was further analyzed by 1D and 2D NMR spectroscopy, mass spectrometry,a nd collision cross-section analysis.N ew routes to molecular encapsulation can be envisioned.
Metal-organic frameworks (MOFs) deposited from solution have the potential to form 2-dimensional supramolecular thin films suitable for molecular electronic applications. However, the main challenges lie in achieving selective attachment to the substrate surface, and the integration of organic conductive ligands into the MOF structure to achieve conductivity. The presented results demonstrate that photoemission spectroscopy combined with preparation in a system-attached glovebox can be used to characterize the electronic structure of such systems. The presented results demonstrate that porphyrin-based 2D MOF structures can be produced and that they exhibit similar electronic structure to that of corresponding conventional porphyrin thin films. Porphyrin MOF multilayer thin films were grown on Au substrates prefunctionalized with 4-mercaptopyridine (MP) via incubation in a glovebox, which was connected to an ultrahigh vacuum system outfitted with photoelectron spectroscopy. The thin film growth process was carried out in several sequential steps. In between individual steps the surface was characterized by photoemission spectroscopy to determine the valence bands and evaluate the growth mode of the film. A comprehensive evaluation of X-ray photoemission spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and inverse photoemission spectroscopy (IPES) data was performed and correlated with density functional theory (DFT) calculations of the density of states (DOS) of the films involved to yield the molecular-level insights into the growth and the electronic properties of MOF-based 2D thin films.
Described for the first time is that carbon dioxide (CO2) can be successfully inserted into aryl C−H bonds of the backbone of a metal–organic framework (MOF) to generate free carboxylate groups, which serve as Brønsted acid sites for efficiently catalyzing the methanolysis of epoxides. The work delineates the very first example of utilizing CO2 for heterogeneous C−H activation and carboxylation reactions on MOFs, and opens a new avenue for CO2 chemical transformations under mild reaction conditions.
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