Although lanthanoid metal–organic frameworks (Ln-MOFs) have been widely developed for white light-emitting diodes (WLEDs), the color rendering index (CRI) values are still lower than 80. To overcome this limitation, a series of CDs/Ln-MOFs hybrids, namely, CDs-2@Ln-MOF, CDs-3@Ln-MOF, and CDs-4@Ln-MOF containing blue-emitting CDs and yellow-emitting bimetallic [(Eu1.22Tb0.78(1,4-phda)3(H2O)]­(H2O)2 were prepared via sonication at room temperature to restrict the self-quenching of CDs in composite materials. The as-synthesized composite materials were investigated by Fourier transform infrared, powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and photoluminescence. The luminescent color of the materials can be adjusted by varying the amount of CDs and excitation wavelengths. The resulting CDs-3@Ln-MOF achieved excellent CRI up to 93 with the ideal Commission International ed’Eclairage coordinate (0.334, 0.334) and appropriate correlated color temperature (CCT) (5443 K). In addition, the tunable multicolored luminescence based on single and bimetallic Eu x Tb2–x (1,4-phda)3(H2O)]­(H2O)2, x = 0, 0.73, 1.22, 1.57, 1.94, and 2, were applied as the luminescent security inks for anti-counterfeiting application through encoding/decoding and rewritable data.

A simple, rapid, highly selective, and real-time determination of water is urgently required for preventing danger from water contamination in materials. Herein, the excited-state proton transfer (ESPT) concept-based luminescent sensor [Cd 2 (2,5-tpt)(4,5-idc)(H 2 O) 4 ] (1) (2,5-tpt = 2,5-dihydroxyterephthalic acid and 4,5-idc = 4,5-imidazoledicarboxylic acid) has been designed for discriminative detection via enol−keto tautomerism. To improve the sensitivity, two-dimensional (2D) nanosheets of 1 have been synthesized by topdown liquid ultrasonic exfoliation technology for sensing water in dimethylformamide, which lead to fast detection (<30 s), high selectivity, broad-range detection (0−50% v/v), and a low detection limit value (0.25% v/v). This sensor can serve dual sensing mechanisms along with a luminescent color change via shifted emission (green→yellow) in low water content and a turn-off method in high water content. For ease of use, the test-strip paperbased 2D nanosheets of 1 have been prepared and applied for water detection with long-term stability, pH stability, and good reusability. On-site water detection in real time can be evaluated using a smartphone color-scanning application for quantitative scanometric assays coupled with test-strip paper-based 2D nanosheets of 1. Also, 1 can be utilized for a colorimetric luminescent thermometer in the ranges of physiological and high temperature with good linearity and recyclability.

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A coordination complex, lithium hepta­(i-butyl)­silsesquioxane trisilanolate (1; Li-T7), a stable intermediate in silsesquioxane (SQ) syntheses, was successfully isolated in 65% yield and found to be highly soluble in nonpolar solvents such as hexane. The structure of Li-T7 was confirmed by NMR, IR spectroscopy, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, electrospray ionization mass spectrometry, and computational simulation, providing detailed elucidation of the intermolecular self-association of the SQ cage with a box-shaped Li6O6 polyhedron through strong coordination bonds. After acid treatment, Li-T7 undergoes lithium–proton cationic exchange, yielding hepta­(i-butyl)­silsesquioxane trisilanol (2; H-T7) quantitatively. The high yield of H-T7 seems to be influenced by Li–O bonding in the Li-T7 complex that affects the selective formation of hepta­(i-butyl)­silsesquioxane trisilanolate and the bulky i-butyl groups which may prevent decomposition or SQ cage-rearrangement even at reflux under alkaline conditions. Single-crystal X-ray crystallography confirms the presence of the dumbbell-shaped SQ partial cages through strong intermolecular hydrogen bonds. Interestingly, lowering the polarity of the reaction solution by adding dichloromethane results in formation of the cubic octa­(i-butyl)­silsesquioxane (3; T8) cage in a good yield (47%), which is isolated by crystallization from the reaction solution.

Three new supramolecular metal-coordination architectures [M(H2O)4(ampyz)2][M(H2O)6](SO4)2(H2O)2 (M = Co (1), Fe (2), and mixed Co/Fe (3); ampyz = 2-aminopyrazine) and a Cd(II) coordination polymer [Cd(ampyz)(H2O)2(SO4)]n(H2O)n (4) were synthesized by layered diffusion and structurally characterized. Compounds 1-3 are isomorphous. Monomeric complex units [M(H2O)4(ampyz)2]2+ are assembled by intermolecular hydrogen bonding and pi-pi stacking via ampyz moieties to build 2D sheets. These layers are linked by intermolecular hydrogen bonding via ampyz ligand, [M(H2O)6]2+ unit, sulfate anion and lattice and coordinated water molecules to stabilize 3D supramolecular structure. Compound 4 shows a 2D coordination network where the sulfato connector and the bridging ampyz link Cd(II) ions. Lattice water molecules are filled in between the layers via the hydrogen bonds stabilizing 3D supramolecular network of 4. Interestingly, compounds 1-3 exhibit water-induced reversible crystal-to-amorphous transformations with chromotropism and compound 4 also shows water-induced reversible structural phase transformation confirmed by spectroscopic techniques, elemental analyses, TGA, and XRPD. These results demonstrate the significant role between coordination bridges and weaker intermolecular interactions for the structural conversion even though 1-3 lack coordination bridges for the maintenance of their structures, however, the weak intermolecular interactions, especially hydrogen bonding, play a key role to the recovery of the crystalline phase.

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