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Disubstituted adamantanes having nitrophenol moieties were examined for their ability to recognize ketone and ester molecules through multiple intermolecular interactions, with the hydroxyl and nitro groups serving as hydrogen bond donors and acceptors. Crystallization of 1,3-bis(2-hydroxy-5-nitrophenyl)adamantane (1) in acetone, 2-butanone, and methyl acetate afforded three inclusion crystals with 1 : 1 stoichiometry. X-ray crystallographic analysis revealed that the hydroxyl groups of 1 engaged in OH⋯O interactions with the guest oxygen atoms in all crystals. Moreover, the guest hydrogen atoms participated in CH⋯O interactions with the host nitro and hydroxyl groups at three, four, or five points. These findings suggest that the guest molecules were captured through interactions with multiple functional groups in a manner resembling that of guest inclusion in enzyme pockets. Crystallization of 1,3-bis(4-hydroxy-3-nitrophenyl)adamantane (2) and 1,3-bis(2-ethoxy-5-nitrophenyl)adamantane (3) in acetone resulted in the formation of guest-free crystals, with NO2⋯NO2 interactions being prominent in the crystal of 3.

The structural effects of energetic coordination compounds (ECCs) influence their composition and performance. By modifying the coordination sites of the ligand and the type of metal, the structure of ECCs can be adjusted, effectively reconciling the contradiction between the performance and sensitivity. In this study, two types of 0D-structured ECCs Cu(2-IMTO)4(ClO4)2(ECCs-1) and Co(2-IMTO)6(ClO4)2(ECCs-2) were innovatively designed using 2-IMTO as the ligand. Structural analysis revealed that ECCs-1 contains a higher amount of [2-IMTO] with a ligand to [ClO4−] ratio of 2 : 1. The results of physical and chemical property tests indicate that both possess acceptable mechanical sensitivity and good thermal stability. Explosion performance calculations revealed that ECCs-1 exhibits higher detonation velocity and pressure (D = 6552 m s−1 and P = 18.7 GPa). Additionally, the laser ignition test results demonstrate that ECCs-1 can be ignited at a lower laser energy threshold (laser power P = 60 W, delay time τ = 10 ms, and ignition energy = 600 mJ).

Two metallo-hydrogen-bonded organic frameworks (MHOFs) were synthesized by self-assembling a phosphate complex and a macrocyclic ligand with three peripheral carboxylic acids. The two MHOFs have different hydrogen-bond linkages and structures, depending on whether the phosphate participates in the hydrogen bonding. The various hydrogen-bonded networks result in different thermal stabilities, BET surface areas, and water vapor uptake capacities of the MHOFs. MHOF-PO4-2, which has more hydrogen bonds and higher porosity, shows better thermal stability and water vapor adsorption than MHOF-PO4-1. This study demonstrates the possibility of constructing diverse and functional MHOFs based on phosphate complexes.

Flexible metal–organic frameworks (MOFs) have been attracting increasing attention in stimuli-responsive applications. However, the effects of the MOF's structural transition on catalysis have been largely unexplored. Herein, the dynamic behaviors and catalytic ability of a flexible bimetallic MOF (i.e., MIL-88B(Fe/Co)) were systematically investigated through density functional theory calculations, which suggested rotary metal nodes and twisted ligands upon lattice contraction, subsequently leading to variable performances in the oxygen evolution reaction as confirmed by the differences in the free energy diagrams. To correlate the catalytic performance with the structural dynamics of the MOFs, partial pair distribution function analysis was carried out, which demonstrated that the short-range order of MIL-88B(Fe/Co) is unaffected by the lattice expansion/contraction, suggesting the intact bond connectivity during the structural transition. The bonding nature of the bimetallic MOF was further investigated through electron localization function analysis, which revealed that structural modulation poses negligible impacts on the bonding interactions in the metal nodes while the contracted structures can cause a closely packed framework. The dependence of the catalytic performance on the dynamic structures demonstrated in this work suggests that the structural transition of the flexible MOFs can be exploited to alter the energy barriers of the elementary steps during the catalysis processes, offering potential avenues to achieving better control over the catalytic pathways for enhanced efficiency.

Five Metal–Organic Frameworks ({[M2(tdc)2(L)2]·2DMF}, tdc = 2,5-thiophenedicarboxylate, M = ZnII (1–Zn), CuII (1–Cu), MnII (1–Mn), {[Zn(oba)(L)]·DMF·H2O} (2–Zn), oba = 4,4′-oxybisbenzoate, and {[Zn2(bpdc)2(L)2]·L}, (3–Zn) bpdc = 4,4′-biphenyldicarboxylate) that incorporate the redox-active 2,5-dipyridylthiazolo[5,4-d]thiazole (DPTzTz) ligand (L) have been synthesised and their electronic properties elucidated. The ligand-based organic radicals were generated using in situ techniques and monitored using a suite of solid-state spectroelectrochemistry techniques. The absence of a near infra-red band (NIR), indicating through-space intervalence charge transfer (IVCT), in all analysed materials suggests that both the inter-ligand distance between cofacial TzTz moieties and the flexibility of the TzTz moiety affect the through-space IVCT.

High-pressure single crystal X-ray diffraction has been used to probe framework–guest interactions in the Co-based metal–organic framework ZIF-67 during compression in 4 : 1 MeOH : EtOH and liquid nitrogen (LN2) pressure-transmitting media. On increasing pressure, the structure undergoes a gate-opening phase transition, characterised by rotation of the 2-methylimidazolate ligand, at 1.57 GPa in MeOH : EtOH and at 0.43 GPa LN2. Adsorption of N2 occurred progressively with increasing pressure into 6 adsorption sites and resulted in the first documented instance of pressure-induced solvatochromism in ZIF-67.

A dual-emission ratiometric fluorescent sensor consisting of a Tb-based metal organic framework (MOF, Tb-DOBDC) has been developed based on an excited-state proton transfer (ESPT) response linker. Due to the ESPT process, Tb-DOBDC exhibits dual emission, which affords a crucial condition for the detection of ammonia as a ratiometric fluorescent sensor.

A new Zn(II) metal–organic framework (MOF) with the formula [Zn(BBIP)(2,6-NDC)]n (JXUST-44, BBIP = 3,5-bis(1H-benzo[d]imidazol-1-yl)pyridine and 2,6-H2NDC = 2,6-naphthalic acid) was synthesized under solvothermal conditions. The adjacent Zn(II) ions are connected by BBIP ligands to form one-dimensional (1D) chains, which are further linked by carboxylate groups of 2,6-NDC2− ligands to obtain a two-dimensional layer structure, resulting in a 2D → 3D polycatenated MOF. JXUST-44 can be simplified as a 4-connected sql topology and shows good chemical stability in a wide pH range from 2 to 12 at room temperature. The fluorescence experiments indicate that JXUST-44 presents sensitive and selective detection of salicylaldehyde (SA), acetylacetone (acac) and H2PO4− with the detection limits of 0.074, 10.311 and 0.011 ppm, respectively. It is worth noting that JXUST-44 shows turn-on fluorescence toward acac and H2PO4−, as well as good recyclability and stability for acac, SA and H2PO4−. Therefore, JXUST-44 can be considered as a good fluorescent sensor for acac, SA and H2PO4−. The sensing mechanism has also been studied in detail.

Mechanically flexible molecular crystals have emerged as a fascinating class of materials with the ability to undergo substantial deformation without compromising their structural integrity. We report here four 3,5-di-tert-butyl salicylaldehyde based di-imine crystals. Crystals 1 and 2 were plastic while crystals 3 and 4 were brittle and elastic, respectively. By changing the length of the intervening linker molecule, structure and packing factors were influenced greatly resulting in the final outcome of mechanical properties. It is possible to fine-tune mechanical properties by changing the length of the linker moiety while keeping the peripheral shape synthons the same. These findings open up new avenues for tailoring the mechanical flexibility of molecular crystals, opening up opportunities for their application in various fields.

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