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The development of photocatalysis is hindered, in part, by the quick recombination of photogenerated carriers and the instability of light sources. In this study, the problem of too-fast electron–hole pair compounding in photocatalysis is effectively regulated by the polarization field of pyroelectric materials using the pyroelectric method. Self-polarized pyroelectric materials that depend on temperature variations can generate usable electrical energy and polarized charge carriers to degrade organic pollutants. Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) is a relaxor ferroelectric material with spontaneous polarization characteristics. The PMN–0.30PT:1 mol%Sm3+ catalyst was prepared by applying the high-temperature solid-state reaction method. Under the dark condition and nine cold–hot cycles of 23 °C–68 °C, using H2O2-assisted PMN–0.30PT:1 mol%Sm3+ as a catalyst, the degradation rate of rhodamine 6G (10 mg L−1) was 94.3 ± 2.5%. In addition, the degradation rates of 88.52% and 64.32% were obtained for rhodamine B (10 mg L−1) and methylene blue (10 mg L−1), respectively. This study provides a new approach to the pyroelectric catalytic degradation of organic pollutants. [ABSTRACT FROM AUTHOR]

In this study, a new cobalt-based metal–organic framework (JLNU-500), [Co2(OH)(PBA)(AIP)]·3DMA·0.75H2O (4-(pyridin-4-yl) benzoic acid (HPBA), 5-aminoisophthalic acid (H2AIP) and N,N-dimethylacetamide (DMA)), was fabricated using a solvothermal method. JLNU-500 has 3D network architecture with 1D nanopore channels. The prepared JLNU-500 can activate peroxymonosulfate (PMS) for Rhodamine B (RhB) dye decolorization. Interestingly, catalyst JLNU-500 exhibited high efficiency for PMS activation, and nearly 100% (above 99.8%) removal of RhB with a high concentration (50.0 mg L−1, 100 mL) was achieved within 6 min. The reaction rate constant of the JLNU-500/PMS system was 1.02 min−1 calculated based on the pseudo-first-order kinetics, which is higher than that of the other reported catalysts. Furthermore, the factors, which could influence PMS activation were also investigated, such as PMS dosage, catalyst dosage, pollutant RhB concentration, reaction temperature and solution pH. More importantly, the radical trapping experiments ferreted out that sulfate (SO4˙−) and hydroxyl (˙OH) radicals were the dominating oxidants in the removal of RhB. Moreover, the possible degradation mechanism was elucidated. This study provides new prospects for fabricating new MOFs that can potentially be employed for high-efficiency catalytic oxidation as heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

One-pot co-precipitation of target molecules e.g. organic dyes and the synthesis of a crystal containing microporous–mesoporous regimes of zeolitic imidazolate frameworks-8 (ZIF-8) are reported. The synthesis method can be used for cationic (rhodamine B (RhB), methylene blue (MB)), and anionic (methyl blue (MeB)) dyes. The crystal growth of the ZIF-8 crystals takes place via an intermediate phase of zinc hydroxyl nitrate (Zn5(OH)8(NO3)2) nanosheets that enabled the adsorption of the target molecules i.e., RhB, MB, and MeB into their layers. The dye molecules play a role during crystal formation. The successful encapsulation of the dye molecules was proved via diffuse reflectance spectroscopy (DRS) and electrochemical measurements e.g., cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). The materials were investigated for carbon dioxide (CO2) adsorption and adenosine triphosphate (ATP) biosensing. ZIF-8, RhB@ZIF-8, MB@ZIF-8, and MeB@ZIF-8 offered CO2 adsorption capacities of 0.80, 0.84, 0.85, and 0.53 mmol g−1, respectively. The encapsulated cationic molecules improved the adsorption performance compared to anionic molecules inside the crystal. The materials were also tested as a fluorescent probe for ATP biosensing. The simple synthesis procedure offered new materials with tunable surface properties and the potential for multi-functional applications. [ABSTRACT FROM AUTHOR]

Multiple emission metal–organic frameworks (MOFs) are superior materials for ratiometric fluorescence sensing and visible detection applications. The guest-encapsulation strategy is a simple method for the integration of the open structure of MOFs and the abundant choice of emissive guests. Herein, we reveal the factors that affect the performance of host–guest multi-emission MOFs based on the choice of ligands, metal nodes, and guest dyes. The size of organic dyes is often larger than 1 nm, which is incompatible with the small pores of traditional MOFs. Therefore, we selected a flexible ligand, i.e., 1,3,5-tris(5-methoxy-1,3-benzene dicarboxylic acid)benzene (L), to enlarge the pore size of the MOF to 18 Å. Energy transfer may occur from the ligand and guest dye to the metal nodes; thus, we selected the Gd3+ ion because of its high excited state level. L and Gd3+ ions were used to form the Gd–L MOF with the pore size of 18 Å, as revealed by the single crystal result. Rhodamine B (RhB), as the guest dye with the size of 15.9 × 11.8 × 5.6 Å3, was encapsulated in Gd–L MOF, which was denoted as RhB@MOF. The matched size between RhB and the MOF pore and the breathing effect of the flexible MOF effectively prevented the leakage of RhB. Accordingly, dual emission was observed at 360 nm and 583 nm under the excitation of 290 nm from RhB@MOF. Alternatively, Cu2+ quenched the emission at 360 nm due to the electron transfer process, while Fe3+ interacted with both L and RhB, and thus quenched the two emissions simultaneously. However, other metal ions showed little effect on the two emissions. Consequently, the differentiation between Cu2+ and Fe3+ as well as them from other metal ions was realized with the dual-emission MOF. Thus, the guest-encapsulation strategy is simple and flexible ligands are efficient to encapsulate molecular dyes for dual-emission MOFs to improve their sensing performance, while flexible ligands are powerful to enhance the capacity and extend the applications of MOFs. [ABSTRACT FROM AUTHOR]

A novel 2D zinc(II) metal–organic framework, formulated as [Zn(L)(H2O)]·H2O (1) (H2L = 4-(pyridine-4-yl) phthalic acid), has been successfully obtained under solvothermal conditions. This metal–organic framework (MOF) material exhibits efficient photocatalytic activity towards the degradation of organic dyes in the absence of any photosensitizer or cocatalyst. Its catalytic performance for rhodamine B (RhB) and methyl orange (MO) degradation was superior to most reported MOFs with a degradation efficiency of 98.5% for RhB and 83.8% for MO within 120 min in the absence of H2O2, which could be attributed to its high efficiency in generating ·O2− (an effective oxidant for the degradation of dyes). The possible mechanism of the reaction was discussed in detail. In addition, 1 shows stable catalytic efficiency after five reaction cycles, which indicates that 1 exhibits efficient catalytic activity and good reusability toward the degradation of organic dyes, enabling it to be a potential candidate for environmental governance. [ABSTRACT FROM AUTHOR]

Chalcogenolate clusters can be interlinked with organic linkers into semiconducting coordination polymers with photocatalytic properties. Here, discrete clusters of Cd8S(SPh)14(DMF)3 were interlinked with 4,4′-bipyridine into a one dimensional coordination polymer of [Cd8S(SPh)14(DMF)(bpy)]n with helical chains. A stepwise mechanism for the assembly of the coordination polymer in DMF was revealed by an ex situ dynamic light scattering study. The cluster was electrostatically neutral and showed a penta-supertetrahedral structure. During the assembly each cluster was interlinked with two 4,4′-bipyridine molecules, which replaced the two terminal DMF molecules of the clusters. In their solid-state forms, the cluster and the coordination polymer were semiconductors with wide band gaps of 3.08 and 2.80 ev. They photocatalytically degraded rhodamine B and methylene blue in aqueous solutions. The moderate conditions used for the synthesis could allow for further in situ studies of the reaction-assembly of related clusters and coordination polymers. [ABSTRACT FROM AUTHOR]