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Photochromic materials coupled with photoswitchable luminescence functionalities are of particular interest due to their potential applications in switches and optical memory devices. However, the construction of such materials, especially those with two-color emission states, is still challenging. In this context, a rare Zn7 cluster-based host–guest MOF material, (bbmp)[Zn7(IPA)6(OH)4(H2O)2] (1) (H2IPA = isophthalic acid, bbmp·2I = 4,4′-([1,1′-biphenyl]-4,4′-diyl)bis(1-methylpyridin-1-ium) diiodide), was prepared by encapsulating an organic cation into an anionic MOF produced from zinc cations and isophthalic acid ligands, which exhibits reversible naked detectable photochromic properties varying from yellow to green upon UV-Vis light irradiation. The photoactive guest bbmp2+ and the short O⋯N+ distances between the oxygen atoms of the carboxylate groups and the pyridine ring play a crucial role in the photochromism of this compound. More interestingly, the luminescence color of this cluster-based host–guest material can be reversibly switched from green to blue upon irradiation, exhibiting photoswitchable luminescence properties. [ABSTRACT FROM AUTHOR]

The incorporation of photochromic units into metal–organic frameworks (MOFs) is of particular interest due to their ability to endow the MOFs with extra functions such as photomodulated fluorescence, photomagnetism, and photomodulated electrical conductivity. In this work, a π-conjugated electron-deficient viologen ligand was assembled with La3+, resulting in a stable cationic MOF with one-dimensional channels, namely [La(bdpbpy)(H2O)2]·NO3·5H2O (1-NO3) (H4bdpbpy·2Cl = 1,1′-bis(3,5-dicarboxyphenyl)-4,4′-bipyridinium dichloride). As expected, 1-NO3 exhibits photochromism accompanied by an obvious color change from yellow to brown under UV-vis light irradiation. Remarkably, the water stable cationic framework of 1-NO3 acts as an efficient and selective trap for toxic dichromate through ion-exchange. The π-conjugated electron-deficient viologen ligand in the framework can provide extra affinity for iodine adsorption, and thus 1-NO3 exhibits sorption behaviours for iodine molecules. More importantly, the iodine adsorption capacity of 1-NO3 was significantly reduced when it was irradiated by UV-vis light. This is attributed to the photoinduced electron transfer (PET) changing the original charge distribution of the bipyridinium moieties on the channel and weakening the affinity for the N+⋯I–I interaction. This work breaks through the traditional design strategy to construct MOF adsorbent materials with controllable adsorption capacity. [ABSTRACT FROM AUTHOR]

As a new generation of semiconductor reinforcements, fluorescent carbon dots have unpredictable and potential applications in bioimaging, photocatalysis, and optoelectronic devices. This work shows an environmentally friendly process for carbon dots preparation using citric acid monohydrate and urea. The influence of different parameters on luminous property was carefully studied based on the photoluminescence intensity measurement, including synthesis temperature, time and the concentration of carbon sources and deactivator. Then the synthesized products were further characterized by TEM, FT-IR, XPS, UV-vis, and XRD. Highest fluorescence intensity could be achieved under the carbon sources and deactivator concentration of 0.3 mol/L and 1 mol/L, respectively, in a total reaction system of 40 ml at 190 °C for 18 hours. The screening analysis revealed that synthesis temperature has a strong correlation with the photoluminescence intensity. This study provides further insights into designing high fluorescent performance for carbon dots preparation. [ABSTRACT FROM AUTHOR]

• Two isomeric metal-organic frameworks are prepared based on naphthalenediimide and naphthalenedicarboxylic acid. • Complexes 1 and 2 exhibit different photochromism and photocontrolled luminescence upon UV–Vis light irradiation. • Noncovalent interactions play an important role in the photochromic properties of MOFs. As a class of special type materials, photochromic metal-organic frameworks (MOFs) have attracted extensive attention because their usually show interesting color changes and coupled with the variation of some chemical and physical properties under light irradiation. In order to study the effect of secondary building on the photochromism of MOFs, two isomeric naphthalenediimide-based MOFs with different secondary building linkers, namely [Zn 2 (DPNDI)(2,6-NDC) 2 ] (1) and [Zn 2 (DPNDI)(1,4-NDC) 2 ] (2) (DPNDI = N, N '-di(3-pyridyl)-1,4,5,8-naphthalenediimide, 1,4-H 2 NDC = 1,4-naphthalenedicarboxylic acid, 2,6-H 2 NDC = 2,6-naphthalenedicarboxylic acid), were synthesized via solvothermal reaction and the structure were characterized by single-crystal X-ray diffraction, IR and TGA. Owing to the different C H···π interactions between the naphthalene moieties of dicarboxylic acid and electron-deficient DPNDI ligand, they showed different photochromic behaviors and photocontrolled luminescence upon ultraviolet-visible irradiation. Specifically, complex 2 was photochromic but complex 1 was not. The difference can be ascribed to the larger C H···π interaction in complex 1 than in complex 2. This work is expected to provide a new perspective for designing novel photochromic MOF materials Two isomeric naphthalenediimide-based MOFs with different secondary building linkers have been prepared, which exhibit different photochromic behaviors and photocontrolled luminescence upon ultraviolet-visible irradiation. [Display omitted] [ABSTRACT FROM AUTHOR]

The rational construction and modulation of charge-transfer based fluorescence materials in host-guest systems by virtue of donor–acceptor interactions remains a challenge owing to the elaborate self-assembly process of acceptor and donor components. Taking into account the design principles of the host-guest system, a well-defined MOF with electron-deficient properties should be an ideal host for the building of charge-transfer based fluorescence materials. Herein, an electron-deficient MOF host, [Cd 3 (NDC) 3 (tpt) 2 (H 2 O) 3 ] (1) (H 2 NDC = 1,4-naphthalenedicarboxylic acid, tpt = 2,4,6-tri(4-pyridinyl)-1,3,5-triazine), and a corresponding series of host-guest materials 1 ⊃guest (guest = phenanthrene for 2 , anthracene for 3 , pyrene for 4 , triphenylene for 5) with charge-transfer based fluorescence were successfully fabricated via the donor–acceptor interactions. Profiting from the clear electron-rich guests to electron-deficient MOF framework charge transfer interactions, the host-guest materials exhibit color-tunable emission over a wide range by rational selection of guest molecules. Furthermore, the electronic structure calculations reveal that the multicolor emission of the newly synthesized MOF materials depends on the HOMO energy level/ionization potential of guests. This work provides a hopeful strategy for the assembly of various novel charge transfer fluorescent materials as potential luminophores. A series of host-guest MOF materials were successfully fabricated by virtue of donor-acceptor interactions, which exhibit color-tunable emissions in a wide wavelength range by rational selection of guest molecules. [Display omitted] • A MOF host based on electron-deficient triazine derivative was prepared. • Four host-guest materials were fabricated via the donor–acceptor interactions. • The host-guest materials exhibit guest-dependent luminescent properties. • Emission of host-guest materials depending on the ionization potential of guests. [ABSTRACT FROM AUTHOR]

Porous lanthanide-transition heterometallic metal-organic frameworks (MOFs) as a subclass of porous hybrid materials have attracted considerable attention as a new advance in the research on MOFs. However, rationally designing and constructing heterometallic MOFs with desirable properties remains a challenging task. In this work, involving the heterometallic cooperative crystallization method, a novel europium-cadmium MOF based on a zwitterionic carboxylate ligand, [EuCd(pbbp) 2 (SO 4) 2 Cl 2 (H 2 O) 3 ] (1), (H 2 pbbp·2Cl ​= ​1,1'-(1,4-phenylene-bis(methylene))-bis(3-carboxy pyridinium) dichloride), has been solvothermally synthesized. Complex 1 was characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy, and thermogravimetric analysis. The structure of complex 1 consists of Eu–Cd heterometallic chains with one-dimensional channels. Complex 1 shows interesting excitation-dependent luminescence at room temperature. The gas adsorption studies show that complex 1 exhibits highly selective adsorption of CO 2 over N 2 and H 2 under ambient conditions, which may be caused by the stronger interaction of CO 2 with the positively charged pyridinium functional groups. In addition, the photocatalytic activity studies indicate that complex 1 shows good activity in rhodamine B dye degradation. A europium-cadmium MOF based on a zwitterionic carboxylate ligand has been solvothermally synthesized, which exhibits interesting excitation-dependent luminescence, highly adsorption of CO 2 under ambient conditions, and good photocatalytic activity in rhodamine B dye degradation. [Display omitted] • A europium-cadmium heterometal-organic framework was prepared. • Complex 1 exhibit excitation-dependent luminescence at room temperature. • Complex 1 shows the good photocatalytic activity for degradation of rhodamine B. • Gas adsorption was applied to study the porosity. [ABSTRACT FROM AUTHOR]

A feasible method to construction multifunctional hybrid compounds is the incorporation of appropriate functional inorganic and organic components through self-assembly. Naphthalene diimides (NDIs) and polyoxometalates (POMs) are two versatile building blocks that have been used in many fields. In this paper, self-assembly of electron-deficient NDI ligand and POM resulted in an organic-inorganic hybrid compound, [Ce 2 (BINDI)(DMF) 8 ]·[Mo 6 O 19 ] (1), (H 4 BINDI = N , N ′-bis(5-isophthalic acid)-1,4,5,8-naphthalene diimide), with segregated Mo 6 O 19 2− polyanions and two-dimensional cationic coordination network. Because of the photochemical activities of organic and inorganic components, this hybrid compound exhibits interesting reversible photochromic behavior under ultraviolet–visible light irradiation. XRD, EPR, and XPS studies demonstrated that the photochromic behavior resulting from the coaction of NDI and Mo 6 O 19 2− polyanions. Moreover, this hybrid material shows excellent photocatalytic degradation activity toward the methylene blue (MB) dye under visible light irradiation. [Display omitted] • A polyoxometalate/naphthalenediimide hybrid structure is prepared. • Compound 1 shows fast-responsive reversible photochromism. • Photoinduced electron-transfer generate Mo5+ and NDI radicals. • Compound 1 exhibits excellent photocatalytic activity for degradation of methylene blue. [ABSTRACT FROM AUTHOR]

• A MOF based on electron-deficient naphthalene diimide dye is prepared. • The anion–π interactions between two-dimensional network and W6O192– is observed. • Complex 1 exhibits eye-detectable fast-responsive reversible photochromism and photoresponsive luminescence. • Photoinduced electron-transfer produces NDI radicals and W5+ species. Metal-organic frameworks that contain photoactive organic ligands or photoactive inorganic components are an emerging class of multifunctional hybrid materials that in recent years has gradually become an ideal platform for building photochromic complexes. In this paper, a metal-organic framework based on naphthalene diimide (NDI) ligand with Lindqvist-type W 6 O 19 2– polyanions, [Ce 2 (BINDI) (DMF) 8 ]·[W 6 O 19 ] (1), (H 4 BINDI = N, N '-bis(5-isophthalic acid)-1,4,5,8-naphthalene diimide) was synthesized and systematically characterized. It displays a cationic two-dimensional grid coordination network, featuring anion–π interactions between W 6 O 19 2– and expanded π–electron deficient naphthalene diimide (NDI) moieties. Moreover, because of the presence of electron-deficient NDI moieties and photoactive W 6 O 19 2–, this complex exhibits fast responsive reversible photochromism and photoresponsive tunable luminescence. UV–Vis, IR, PXRD, EPR, and XPS spectral studies indicate that the obviously photochromic phenomenon of complex 1 is derived from photoinduced electron-transfer form NDI radicals and W5+ species. [Display omitted]. [ABSTRACT FROM AUTHOR]

The encapsulation of photoactive guests into a metal-organic framework is advantageous in endowing extra functionalities such as photochromism and photoswitchable luminescence. In this paper, a host-guest MOF material, [Zn 3 (IPA) 4 ​MV] (1) (H 2 IPA ​= ​isophthalic acid, MV·2NO 3 ​= ​1,1'-dimethyl-(4,4'-bipyridine)-1,1'-diium dinitrate) has been constructed by encapsulating simplest methyl viologen guest into the anionic MOF framework. This material exhibits reversible naked-eye detectable photochromic properties varying from colorless to blue upon UV–Vis light irradiation. The MV2+ and the short O⋯N distance between the oxygen atom and pyridine ring of MV2+ play a crucial role in the photochromism of this compound. This host-guest MOF compound shows photoswitchable luminescent properties in the solid state. More interestingly, this host-guest MOF material can be deposited on filter paper and can be employed as inkless print material by controlling the UV–Vis light irradiation with the stencil. A novel MOF-based host-guest compound was prepared by incorporating the photoactive methyl viologen into the anionic framework, which exhibit photochromism upon UV–Vis light irradiation and photocontrolled luminescence. Moreover, this compound can be used as inkless and erasable print media. [Display omitted] • A host-guest compound was prepared by incorporating the viologen into the anionic MOFs. • Compound 1 exhibits fast-responsive photochromism and reversible luminescence switching upon UV–Vis light irradiation. • Compound ​ 1 ​can be employed as inkless and erasable print media by controlling the UV-Vis light irradiation. [ABSTRACT FROM AUTHOR]

The tunable luminescent materials based on photochromic reactions have received considerable interest due to its potential applications in switches and optical memory devices. However, constructing such materials with ideal properties remains a challenge. In this context, two rare viologen-based host guest materials, 2[MV]·[Zn 6 (PMA) 4 (H 2 O) 4 ] (1), 2[PBM]·[Zn 2 (PMA) 2 (H 2 O) 6 ] (2), (MV·2NO 3 ​= ​1,1'-dimethyl-(4,4'-bipyridine)-1,1'-diium dinitrate; PBM·2NO 3 ​= ​4,4'-(1,4-phenylene)bis(1-methylpyridin-1-ium) dinitrate; H 2 PMA ​= ​pyromellitic acid), have been prepared by encapsulating viologen derivatives into the anionic metal-organic frameworks produced from pyromellitic acid ligands and zinc cations. Due to the presence of photoactive guest MV2+/PBM2+ and the short O⋯N+ distances between the oxygen atom of carboxylate groups and pyridine ring of guest, both complexes display fast-responsive reversible naked photochromism from colorless to blue or yellow upon UV–Vis irradiation At the same time, these host-guest materials exhibit good fluorescence emission behavior and their fluorescence can be reversible modulation under light irradiation. These are rare examples of fluorescence switching materials based on host-guest system that involve the electron-transfer photochromic process. Two novel MOF-based host-guest compounds were prepared by incorporating the photoactive viologen derivatives into the anionic framework, which exhibit photochromism upon UV–Vis light irradiation and photocontrolled luminescence. [Display omitted] ● Two host-guest complexes are prepared by incorporating the viologen derivatives into the anionic MOFs. ● Complexes 1 and 2 exhibit fast-responsive photochromism upon UV–Vis light irradiation. ● Complexes 1 and 2 show good luminescent emission and reversible luminescence switching. [ABSTRACT FROM AUTHOR]

Exploring desirable and photostable homostructured catalysts is an explosive scientific hotspot for energy crisis and wastewater treatment. Efficient pollutants removal from wastewater is an attractive route to sustainable development. We here present an ideal photocatalyst that incorporates both g-C 3 N 4 and TiO 2 sheets (TNs), creating a novel nanomaterial of the type g-C 3 N 4 /TNs catalyst. The obtained photocatalyst can accelerate the interfacial charge transfer rate. Subsequently, we prepared 2:1O−-g-C 3 N 4 /TNs photocatalysts by H 2 treatment, which not only generated more active defects on 2:1O−-g-C 3 N 4 /TNs surface, but also produced oxygen vacancies. As measured by the degradation of CR (CR), the as-prepared g-C 3 N 4 /TNs samples perform outstanding removal properties due to high photocurrent response under visible light irradiation, which are transcend than bulk g-C 3 N 4 or pure TNs separately. Specially, the obtained 2:1O−-g-C 3 N 4 /TNs catalysts exhibit the highest photocatalytic rate for decomposition of CR (86.7%, 2 h), which was 107.5, 7.167, and 1.43 times higher than that of TNs, g-C 3 N 4 , and 2:1 g-C 3 N 4 /TNs. The decisive factor in enhancing the photocatalytic ability of this optimal sample is the richly available reaction sites exposed by hydrogenation process. [Display omitted] • TiO 2 supported over g-C 3 N 4 resulted in enhanced removal of Congo-red. • H 2 treatment can generate abundant active sites and produce oxygen vacancies. • The hydrogenated 2:1 g-C 3 N 4 /TiO 2 exhibited the highest photodegradation rate of Congo-red (86.7%, 2 h). • The active sites and oxygen vacancies play an important role in enhanced and stable activity. [ABSTRACT FROM AUTHOR]

Controlled deposition of co-catalysts on the requisite surfaces is highly crucial for myriad applications related to photocatalysis. However, the complex preparation process and different precursors may affect their photocatalytic performance. Here, carbon dots (CDs)-doped TiO 2 nanosheets (CDs/TNs), which possess high photocatalytic activity and wastewater purification ability, were synthesized using different precursors of CDs (citric acid: CA and ammonium citrate: AC). Then, the prepared CA-CDs/TNs and AC-CDs/TNs were compared using different techniques. The results illustrated that the particle sizes for AC-CDs and CA-CDs are 1.50 ± 0.204 nm and 3.98 ± 0.37 nm. Compared with AC-CDs, the lattice spacing of CA-CDs is 0.195 nm, which is narrower than that of AC-CDs. Meanwhile, CDs are successfully doped on the surface of TNs. Both CA-CDs/TNs and AC-CDs/TNs exhibit outstanding photodegradation activity and robust stability. And the photocatalytic performance of CDs/TNs increases firstly and then decreases with increasing the amount of CDs. Specially, 0.2CA-CDs/TNs exhibit the highest degradation efficiency, having removed ~91.6% of CR (2 h), 90.2% of RhB (2 h) and 96.1% of TC (1 h), which are 5.70%, 7.13% and 6.7% higher than that of 0.2AC-CDs/TNs. Meanwhile, the removal performance of bright green (BG) and azorubine (ZB) were also performed. As expected, CDs activate TNs to remove BG (91.08% within 150 min) and ZB (86.69% within 4 h) more efficiently. Finally, the feasible degradation pathways of the pollutants are discussed. • ZB and BG were removed in the two CDs/TNs system under visible light. • Carbon dots with different precursors were grew on TiO 2 surface. • The degradation ability of CDs/TNs was compared. • Molecular mechanism of pollutants was constructed. [ABSTRACT FROM AUTHOR]

• EPO promotes axonal sprouting in a dose-dependent manner. • GDF10 is the executor of EPO-mediated axonal sprouting. • EPO induces GDF10 expression through JAK2-PI3K-NF-κB signaling. Erythropoietin (EPO) has an exact neuroprotective effect on stroke. However, it remains unknown whether it participates in axonal sprouting after neuron damage. Growth and differentiation factor 10 (GDF10) has been shown to be a trigger of axonal sprouting after stroke. Hence, it was hypothesized that EPO promotes axonal sprouting mainly through GDF10. In the present in vitro experiment, it was found that EPO could promote axonal sprouting and GDF10 expression in a dose–dependent manner. The knockdown of GDF10 using siRNA abolished the effect of EPO-mediated axonal sprouting, indicating that GDF10 is the executor of EPO-mediated axonal sprouting. The treatment of neurons with nuclear factor-kappaB (NF-κB) inhibitor JSH-23 could inhibit the accumulation of NF-κB phospho-p65 (p-p65) in the nucleus, the upregualtion of GDF10 and extending of axonal length. Furthermore, the addition of Janus kinase 2 (JAK2) inhibitor CEP-33779 or phosphoinositide 3-kinase (PI3K) inhibitor LY294002 to the culture medium also blocked the nuclear translocation of p-p65, the expression of GDF10, and axonal sprouting, suggesting that EPO induces axonal sprouting via activating cellular JAK2 and PI3K signaling. Impeding JAK2 signaling with CEP-33779 can suppress the phosphorylation of PI3K, and this confirms that the upstream of PI3K signaling is JAK2. These present results provide a novel insight into the role of EPO and the molecular mechanism of axonal sprouting, which is beneficial for the development of novel approaches for neurological recovery after brain injury, including stroke. [ABSTRACT FROM AUTHOR]