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The structural characterization of metal-organic frameworks(MOFs) by powder X-ray diffraction can be challenging. Even more difficultare studies of guest solvent or gas molecules inside the MOF pores. Hence, recently we successfully designed several new approaches forstructural investigations of porous MOFs. These methods use structureenvelopes, which can be easily generated from the structure factorsof a few (1-10) of the most intense low index reflections. However, the most interesting results have been found by using differenceenvelope density (DED) analysis. DED can be produced by taking thedifference between observed and calculated structure envelope densities. The generation and analysis of DED maps are straightforward but allowstudying guest molecules in the pores of MOFs by using routine powderX-ray diffraction data. Examples of DED used for studies of solventmolecule location, porosity activation, and gas loading are presentedherein. We show that DED analysis is an important technique in thestudy of host-guest properties in MOFs by providing position, shape, and approximate occupancy of molecules in the MOF pores. [ABSTRACT FROM AUTHOR]

Despite being the fifth most abundant element in the atmosphere, neon has never been observed in an organic or metal–organic environment. This study shows the adsorption of this highly unreactive element within such an environment and reveals the first crystallographic observation of an interaction between neon and a transition metal. [ABSTRACT FROM AUTHOR]

Sensitized upconversion is explored in three metal–organic frameworks (MOFs) constructed from the anthracene dicarboxylate (ADC) derivatives and zirconium nodes, 9,10-ADC (9,10-MOF), 2,6-ADC (2,6-MOF) and 1,4-ADC (1,4-MOF). Selective excitation of surface-bound Pd(ii) mesoporphyrin IX (PdMP) gives rise to delayed fluorescence (τ = 370 ± 30 ns) from anthracene in the 9,10-MOF. The overall upconversion efficiency of the Pd@9,10-MOF is 0.46 ± 0.05% with a threshold intensity of 104 ± 26 mW cm−2. [ABSTRACT FROM AUTHOR]

The application of atomic layer deposition (ALD) to metal-organic frameworks (MOFs) offers a promising new approach to synthesize designer functional materials with atomic precision. While ALD on flat substrates is well established, the complexity of the pore architecture and surface chemistry in MOFs present new challenges. Through in situ synchrotron X-ray powder diffraction, we visualize how the deposited atoms are localized and redistribute within the MOF during ALD. We demonstrate that the ALD is regioselective, with preferential deposition of oxy-Zn(II) species within the small pores of NU-1000. Complementary density functional calculations indicate that this startling regioselectivity is driven by dispersion interactions associated with the preferential adsorption sites for the organometallic precursors prior to reaction. [ABSTRACT FROM AUTHOR]

The prototypical single-molecule magnet (SMM) molecule [Mn12O12(O2CCH3)16(OH2)4] was incorporated under mild conditions into a highly porous metal-organic framework (MOF) matrix as a proof of principle for controlled nanostructuring of SMMs. Four independent experiments revealed that the SMM clusters were successfully loaded in the MOF pores, namely synchrotron-based powder diffraction, physisorption analysis, and in-depth magnetic and thermal analyses. The results provide incontrovertible evidence that the magnetic composite, SMM@MOF, combines key SMM properties with the functional properties of MOFs. Most importantly, the incorporated SMMs exhibit a significantly enhanced thermal stability with SMM loading advantageously occurring at the periphery of the bulk MOF crystals with only a single SMM molecule isolated in the transverse direction of the pores. [ABSTRACT FROM AUTHOR]

Through topological rationalization, a zeotype mesoporous Zr-containing metal-organic framework (MOF), namely PCN-777, has been designed and synthesized. PCN-777 exhibits the largest cage size of 3.8 nm and the highest pore volume of 2.8 cm3 g−1 among reported Zr-MOFs. Moreover, PCN-777 shows excellent stability in aqueous environments, which makes it an ideal candidate as a support to incorporate different functional moieties. Through facile internal surface modification, the interaction between PCN-777 and different guests can be varied to realize efficient immobilization. [ABSTRACT FROM AUTHOR]

Through topological rationalization, a zeotype mesoporous Zr-containing metal-organic framework (MOF), namely PCN-777, has been designed and synthesized. PCN-777 exhibits the largest cage size of 3.8 nm and the highest pore volume of 2.8 cm3 g−1 among reported Zr-MOFs. Moreover, PCN-777 shows excellent stability in aqueous environments, which makes it an ideal candidate as a support to incorporate different functional moieties. Through facile internal surface modification, the interaction between PCN-777 and different guests can be varied to realize efficient immobilization. [ABSTRACT FROM AUTHOR]

We demonstrate that rigidifying the structure of fluorescent linkers by structurally constraining them in metal-organic frameworks (MOFs) to control their conformation effectively tunes the fluorescence energy and enhances the quantum yield. Thus, a new tetraphenylethylene-based zirconium MOF exhibits a deep-blue fluorescent emission at 470 nm with a unity quantum yield (99.9 ± 0.5%) under Ar, representing ca. 3600 cm-1 blue shift and doubled radiative decay efficiency vs the linker precursor. An anomalous increase in the fluorescence lifetime and relative intensity takes place upon heating the solid MOF from cryogenic to ambient temperatures. The origin of these unusual photoluminescence properties is attributed to twisted linker conformation, intramolecular hindrance, and framework rigidity. [ABSTRACT FROM AUTHOR]

A 3D Magnesium MOF PCN-72 has been synthesized from the solvothermal reaction of Mg(NO3)2 and a linear ligand. This MOF has a unique structure with 1-dimensional (1D) channel as well as infinite metal chains, which resembles the topology of MIL-53. It is thermally and moisture stable. In situ powder X-ray diffraction studies reveal its interesting phase transitions under temperature change. Calculation shows that each phase of PCN-72 exhibits unique and unusual thermal expansion properties. After removing coordinated solvent at Mg chains, PCN-72 can selectively adsorb CO2 over N2. [ABSTRACT FROM AUTHOR]