The novel metal-organic framework [(CH₃)₂NH₂]₂[Ce₂(bdc)₄(DMF)₂]·2H₂O (Ce-MOF, H₂bdc-terephthalic acid, DMF-N,N-dimethylformamide) was synthesized by a simple solvothermal method. Ce-MOF has 3D connectivity of bcu type with a dinuclear fragment connected with eight neighbors, while three types of guest species are residing in its pores: water, DMF, and dimethylammonium cations. Dimethylamine was demonstrated to have a decisive templating effect on the formation of Ce-MOF, as its deliberate addition to the solvothermal reaction allows the reproducible synthesis of the new framework. Otherwise, the previously reported MOF Ce₅(bdc)_7.5(DMF)₄ (Ce5) or its composite with nano-CeO₂ (CeO₂@Ce5) was obtained. Various Ce carboxylate precursors and synthetic conditions were explored to evidence the major stability of Ce-MOF and Ce5 within the Ce carboxylate-H₂bdc-DMF system. The choice of precursor impacts the surface area of Ce-MOF and thus its reactivity in an oxidative atmosphere. The in situ PXRD and TG-DTA-MS study of Ce-MOF in a nonoxidative atmosphere demonstrates that it eliminates H₂O and DMF along with (CH₃)₂NH guest species in two distinct stages at 70 and 250 °C, respectively, yielding [Ce₂(bdc)₃(H₂bdc)]. The H₂bdc molecule is removed at 350 °C with the formation of novel modification of Ce₂(bdc)₃, which is stable at least up to 450 °C. According to the total X-ray scattering study with pair distribution function analysis, the most pronounced local structure transformation occurs upon departure of DMF and (CH₃)₂NH guest species, which is in line with the in situ PXRD experiment. In an oxidative atmosphere, Ce-MOF undergoes combustion to CeO₂ at a temperature as low as 390 °C. MOF-derived CeO₂ from Ce-MOF, Ce5, and CeO₂@Ce5 exhibits catalytic activity in the CO oxidation reaction.

Single-phase polycrystalline hydrogrossulars were prepared by the hydrothermal treatment of strätlingite in its mother liquor. Their thermal behavior and structural response were studied by in situ PXRD and ex situ solid-state NMR.

Barium selenocyanate, Ba[SeCN] ₂ , was synthesized from Ba[OH] ₂ and [NH ₄ ][SeCN] in THF. As single crystals suitable for structure determination could not be obtained, the crystal structure was solved from high‐resolution powder X‐ray diffraction (PXRD) data. Variable‐temperature PXRD showed that thermal treatment at 200 °C markedly improves crystallinity and permits reliable indexing and subsequent structure solution. Ba[SeCN] ₂ crystallizes in the monoclinic space group C 2/ c (No. 15; a = 12.0242(2) Å, b = 7.0430(1) Å, c = 7.2515(1) Å, β = 101.3894(11)°) and represents a new structure type. The Ba ²⁺ cation is coordinated by four N and four Se atoms of eight [SeCN] ⁻ anions in the form of a distorted tetragonal antiprism. Raman spectroscopic measurements supported by periodic density functional theory (DFT) calculations enabled assignment of the principal internal vibrational modes of the selenocyanate anion. The present study provides the first detailed structural characterization of a binary alkaline earth metal selenocyanate and expands the family of structurally characterized binary inorganic selenocyanates.

Postsynthetic modification (PSM) is a powerful strategy for modifying properties such as pore environment, stability and catalytic activity in covalent organic frameworks (COFs). While the chemical outcomes of PSMs are well documented, their impact on the underlying crystal lattice is rarely quantified. Yet, when translating modified COF systems toward catalytic applications, such structural changes can impact performance. In this work we interrogate precisely that blind spot for the benchmark electrocatalyst COF-366-Co. We apply three chemical PSM routes to the imine backbone: (i) quinoline cyclization (q-COF-366-Co), (ii) amine reduction (r-COF-366-Co), and (iii) nitrone oxidation (o-COF-366-Co) and investigate chemical as well as structural modifications induced by the functionalization. The catalysts are further investigated toward the electrochemical carbon dioxide reduction reaction in an attempt to decouple the multitude of convoluted aspects that affect catalytic activity, stability and selectivity such as particle size, disorder, strain, catalytic environment, and framework stability. Among the series, q-COF-366-Co showed a higher stability toward CO selectivity over time compared to the pristine COF-366-Co at −0.88 V vs reversible hydrogen electrode (RHE). Investigating q-COF-366-Co further showed, however, that higher functionalization concentrations led to simultaneous increase in disorder and a lower selectivity toward CO during catalysis. This indicates that a balance must be found between functionalization and preservation of crystalline lattice, offering insights into the design importance of maintaining structural coherence when comparing COF-based materials toward applications.

Solid-state studies evaluating intermolecular geometries in methylated nucleobases are not extensively explored. In the course of the present study, we have solved the crystal structures of 1-, 3- and 7-methylated adenines and guanines, including the monohydrate and sesquihydrate forms of 3-methyladenine and 3-methylguanine, respectively, by means of single-crystal X-ray diffraction and synchrotron/laboratory X-ray powder diffraction (XRPD). In situ high temperature XRPD experiments, coupled with differential thermal analysis/thermogravimetry (DTA/TG) measurements, allowed for monitoring crystallographic changes after water removal of N3-methylated compounds, and the discovery of a high temperature polymorph in the case of 3-methyladenine. Our findings indicate that H-bonding schemes describe ribbon planar motifs of molecules in the majority of cases, or linear double-bonded strands of molecules in a few cases. π-π stacking interactions were compared with existing findings of theoretical calculations and existing crystallographic data, showing how N-methylated purine bases follow the trend predicted by Hunter and Sanders, 1990. The present study provides the first systematic experimental insights into the solid state of the presented compounds.