Structure elucidation of a condensed carbon(IV) nitride with a stoichiometry close to C3N4 by electron diffraction reveals a two-dimensional planar heptazine-based network containing isolated melamine molecules in the trigonal voids.

All μ-hydroxyl groups are frequently encountered capping groups found on the external surfaces of various minerals that are often used as fillers in composite materials. Covalent grafting to this functional group would therefore offer a versatile and attractive route to surface modification. The octahedral layer of kaolinite is composed of μ-bridged aluminol groups. In particular, intercalation compounds of kaolinite, where all basal planes are exposed and may be modified, are ideally suited to study the feasibility of such covalent graftings. The huge (internal) specific surface area greatly improves the sensitivity of the analytics and renders kaolinite an ideal model compound. Herein we analyze the mode of bonding of ethylene glycol (EG), intercalated into kaolinite (EG kaolinite), by solid-state NMR techniques. 27 Al MQMAS allows for distinction between intercalated and grafted EG molecules because the chemical surroundings of octahedrally coordinated aluminum nuclei in the layer are significantly changed by the formation of a covalent bond. Moreover, the temperature-dependent dynamics of the EG molecules in the interlamellar space are examined by wide-line solid-state 1 H NMR measurements. The EG molecules perform a circular motion around the covalently bonded hydroxyl group in the interlamellar space. Analysis of the 13 CÀ 27 Al REAPDOR measurement in conjunction with the EG dynamics allows for determination of the 13 C 3 3 3 27 Al distance between octahedral aluminum and the bonded carbon atom of EG. This distance is 3.1 Å. A thorough description of the bonding mode of the EG molecules is provided and proves beyond any doubt the covalent grafting. This suggests that the reactivity of μ-hydroxyl groups, in general, is sufficient to realize a covalent surface modification of a wide range of minerals.

Four new porous CAU-1 derivatives CAU-1-NH 2 ([Al 4 (OH) 2 (OCH 3) 4 (BDC-NH 2) 3 ]?xH 2 O, BDC-NH 2 22 = aminoterephthalate), CAU-1-NH 2 (OH) ([Al 4 (OH) 6 (BDC-NH 2) 3 ]?xH 2 O), CAU-1-NHCH 3 ([Al 4 (OH) 2 (OCH 3) 4 (BDC-NHCH 3) 3 ]?xH 2 O) and CAU-1-NHCOCH 3 ([Al 4 (OH) 2 (OCH 3) 4 (BDC-NHCOCH 3) 3 ]?xH 2 O) all containing an octameric [Al 8 (OH) 4+y (OCH 3) 82y ] 12+ cluster, with y = 0-8, have been obtained by MW-assisted synthesis and post-synthetic modification. The inorganic as well as the organic unit can be modified. Heteronuclear 1 H-15 N, 1 H-13 C and homonuclear 1 H-1 H connectivities determined by solid-state NMR spectroscopy prove the methylation of the NH 2 groups when conventional heating is used. Varying reaction times and temperatures allow controlling the degree of methylation of the amino groups. Short reaction times lead to non-methylated CAU-1 (CAU-1-NH 2), while longer reaction times result in CAU-1-NHCH 3. CAU-1-NH 2 can be modified chemically by using acetic anhydride, and the acetamide derivative CAU-1-NHCOCH 3 is obtained. Thermal treatment permits us to change the composition of the Al-containing unit. Methoxy groups are gradually exchanged by hydroxy groups at 190 uC in air. Solid-state NMR spectra unequivocally demonstrate the presence of the amino groups, as well as the successful post-synthetic modification. Furthermore 1 H-1 H correlation spectra using homonuclear decoupling allow the orientation of the NHCOCH 3 groups within the pores to be unravelled. The influence of time and temperature on the synthesis of CAU-1 was studied by X-ray powder diffraction, elemental analyses, and 1 H liquid-state NMR and IR spectroscopy.

The new Al-based metal-organic framework [Al(13)(OH)(27)(H(2)O)(6)(BDC-NH(2))(3)Cl(6)(C(3)H(7)OH)(6)] denoted CAU-6 (CAU = Christian-Albrechts-Universität) was solvothermally synthesized in 2-propanol and was thoroughly characterized. The framework structure exhibits a unique column-shaped inorganic building unit, which is based on stacked, corner-sharing Al(13)-clusters. The compound exhibits unprecedented hydrophilicity for metal-organic frameworks.

We report the synthesis and characterization of the new switchable Zn‐based zeolitic imidazolate framework (ZIF) [Zn(Im)(aIm)] (1). The high‐throughput investigation of the mixed linker system Zn2+/imidazole (HIm)/2‐phenylazoimidazole (HaIm)/DMF at 85 °C led to 1, which is isostructural to ZIF‐8 and crystallizes in a sodalite (SOD)‐type structure. The preparation was also studied with microwave‐assisted heating and ultrasound‐assisted synthesis. The crystal structure was determined from single‐crystal X‐ray diffraction data. Although Im– and aIm– ions are present in a 1:1 molar ratio, no ordering of the 2‐phenylazo group was observed. Incorporation of the Im– and aIm– linkers as an integral part of the framework structure was confirmed by elemental analysis, 13C and 15N MAS NMR, IR and Raman spectroscopy. In addition, the permanent porosity of 1 was demonstrated by N2 sorption experiments and a specific surface area of SBET = 580 m2 g–1 is observed. The photoswitching properties were investigated by UV/Vis spectroscopy as the cis and trans isomers exhibit different UV absorption spectra. Switching can be achieved by irradiation with UV light (λ = 355 nm), and back‐switching using visible light (λ = 525 nm). Although changes in the UV/Vis spectra are detected, the switching process is only partially reversible.