A convenient colorimetric molecular system constructed by the zinc viologen-carboxylate framework is developed for naked eye detection of instantaneous UV exposure levels. Only narrow-band absorption in UV regions and a unique interpenetrated structure of its colorless crystal enable the system to give a fast response toward UV irradiance with intensity as low as 0.001 mw/cm2.Keywords: crystalline material; metal organic framework; thermal stability; UV photodetector; visible-blind; zinc-viologen framework;

•A luminescent-photocolored molecular system is constructed based on the zinc coordination complex;•Its structure is characterized by single crystal data;•The crystal of 1 shows a new color response from grey to orange under light irradiation;•The photoinduced electron transfer reaction is coupled with an energy transfer process between photoactive components.Tailoring photoinduced color of a donor-acceptor molecular system is achieved by introducing the macrocycle electron-deficient ligand into the structure of a zinc phosphate binuclear unit. Fluorescence quenching occurs accompanying with the light irradiation process due to energy transfer between the photoactive components.Tailoring photoinduced color of a donor-acceptor molecular system is achieved by introducing the macrocycle electron-deficient ligand into the structure of a zinc phosphate binuclear unit. Fluorescence quenching occurs accompanying with the light irradiation process due to energy transfer between the photoactive components.Download high-res image (169KB)Download full-size image

A bifunctional luminescent switch is constructed by introducing a terpyridyl derivative into a hydrogen-bond-assisted layered assembly structure. It exhibits interesting mechanochromic and thermochromic luminescence behaviors with reversible color changes visible to the naked eye from pink to blue-purple upon mechanical grinding and from pink to blue upon heating.

•Interpenetrated nonporous MOF used as precursor to synthesize N-doped hierarchically mesoporous carbon.•Enriched metal ions in MOF are effective in generating mesopores as a pore-forming agent in final carbon.•Carbon yields superior electrocatalytic activity and remarkable anion-insensitivity for ORR.Nitrogen-doped carbon materials with hierarchically mesoporous structure are synthesized in the present work via the pyrolysis of an interpenetrated non-porous metal-organic framework (MOF), viz. [Zn2(TPT)(BDC)2]·H2O (SCUT-11, TPT = tris(4-pyridyl)triazine, BDC = 1,4-benzenedicarboxylate), as the precursor. X-ray diffraction reveals that the synthesized metal-organic framework (MOF) is of high purity of the crystalline phase, and its structure follows our previously reported SCUT-11. This triply-interpenetrated MOF features high density of Zn cations in their interwoven packing structure, which act as effective pore-forming agent to generate mesopores in final carbon. Physicochemical characterizations reveal that the resultant carbon has high specific surface area and bimodal mesopore size distribution, which originate from the removal of metal oxide and/or metal zinc. These textual features favour both oxygen mass transfer and accessibility of catalytically active sites. Electrochemical results confirm that the resultant carbon, synthesized by pyrolysis at 900 °C, shows a superior oxygen reduction reaction (ORR) activity, which is associated with high onset and half-wave potential up to 1.0 and 0.88 V, respectively. Further investigation suggests that the as-synthesized carbon catalyst exhibits a remarkable insensitivity towards anions, like sulphate and phosphate, compared with the Pt counterpart. The above features make this carbon catalyst promising to be widely used in different fuel cell types.Download high-res image (168KB)Download full-size image

•The crystal of a cadmium coordination complex shows tunable photoluminescence emissions.•Its structure is characterized.With the generation of photoinduced radicals, an additional low-energy emission is observed in a photoactive cadmium coordination complex. That cooperates with the high-energy monomer emission of the macrocycle ligand, tunable blue-to-yellowish green photoluminescence emissions are achieved upon variation of photoirradiation time and excitation wavelengths.With photogenerated radicals, tunable blue-to-yellowish green photoluminescence emissions are achieved upon variation of photoirradiation time and excitation wavelengths due to the cooperation of high energy monomer of the macrocycle ligand and low energy of the photoirradiated complex.

A novel Zn-MOF-based photochromic complex with tunable photophysical behavior has been developed. The control of luminescent emission and color can be achieved in a single compound by utilizing suitable molecular self-assembly of luminophore and photochromic component.

•Two new photoactive molecular systems are constructed based on the zinc chloride hybrid complexes.•The crystals of 1 and 2 show interesting photoresponsive behaviors under UV–visible light irradiation.•The structure–property relationship of these two photosensitive halometallate hybrid complexes is investigated.Two new photoinduced electron transfer supramolecular systems based on halometallate hybrid complexes are built by the combination of zinc chloride and N-(3-cyanophenyl)-4,4′-bipyridinium functional blocks. Photogenerated radicals and reversible photochromic cycles are observed for these molecular switches. Their photoresponsive characteristics are associated with the structural arrangements of the donor and acceptor units.Two new photoinduced electron transfer supramolecular systems based on halometallate hybrid complexes are built by the combination of zinc chloride and N-(3-cyanophenyl)-4,4′-bipyridinium functional blocks. Photogenerated radicals and reversible photochromic cycles are observed for these molecular switches. Their photoresponsive characteristics are associated with the structural arrangement modes of the donor and acceptor units.

A dual stimuli-responsive system was constructed by introducing methyl viologen into a luminescent europium–organic framework with a compact packing mode. In addition to absorption and emission properties that are sensitive to both light and heat involving electron/energy transfer processes, the photoactive MOF has a spectral response from UV to the visible region.

A unique hydrothermal selective hydrogenation process is carried out effectively in a simple and friendly way without adding any precious metal catalysts and hydrogen gas from outside. The self-assembly of the hydrogenated product 3-(4-(pyridin-4-yl)piperidin-1-yl) benzoate (PYPDB) with the zinc ion produces a highly stable photoactive complex Zn(PYPDB)2 displaying interesting long range electron transfer behavior in the conjugated ring system.

An investigation into the relationship between structures of three D–A supramolecular systems and their photoresponsive characteristics is presented. Compound 1 [H2CPBPY]·[H2BTEC] and compound 2 [HCPBPY]2·[H2BTEC]·5H2O are prepared with the same starting materials at different pH values and characterized by single crystal X-ray diffraction, powder X-ray diffraction, UV-vis, IR and ESR spectra. Electron-deficient CPBPY moieties and electron-donating BTEC units are linked by hydrogen-bonds and π–π stacking interactions to form the donor–acceptor systems. Under light irradiation, photoactivated electrons can transfer from the donor to the acceptor units in both 1 and 2, giving rise to a long-lived charge-separated state and accompanying an interesting color changing phenomenon. Crystals of 2 allowed to dehydrate at elevated temperature undergo single-crystal to single-crystal transformation to yield 3 [HCPBPY]2·[H2BTEC], accompanied by a drastic change in structural arrangements. For the photocoloration character, compound 1 shows a faster photoresponsive rate than 2 and 3. For the fluorescence properties, compound 1 and 2 both exhibit photoluminescence emission centered at 400 nm, whereas 3 exhibits photoluminescence emission at 520 nm, showing a significant red shift of 120 nm. Their different photoactive characters can be attributed to the connecting, packing modes and the valence states of the functional D–A moieties.

A new hybrid organic zinc phosphate–phosphite with a tris (4-pyridyl) triazine molecule embedded in the cavity of an extra-large 24-ring channel has been synthesized and characterized. A strong luminescence emission is observed, which is due to the close packed array of organic ligands. The covalent coupling of fluorescent and photochromic components builds a novel phosphate-based photoactive dyad system.

A new stable 1D photo-responsive coordination polymer is constructed via introducing a viologen side group to the metal–carboxylate framework. This structural arrangement creates an interesting dual stimuli-responsive molecular system. Coupled with the fluorescence modulation process, a photochromic reaction is induced by energy and electron transfer between the neighbouring donor and acceptor units.

Suitable combination of organic fragments N-(3-carboxyphenyl)-4,4′-bipyridinium and m-benzene dicarboxylate affords a new type photochromic metal–viologen coordination polymer with close packed arrangements. The aggregates build an interesting stable crystalline framework showing long lived color constancy. Repeating cycles of reversible color changes are observed for the molecular switch in air upon photoirradiation.

Keggin polyphosphotungstate cluster was captured by a porous molecular ring with light sensitizing TPT molecules as connectors and copper ions as nodes. The self-assembly reaction gives a stable host–guest supramolecular system, demonstrating efficient heterogeneous photocatalytic behavior for the degradation of methyl orange in near-neutral conditions.

A new type of electron transfer (ET) system was built via the combination of a highly stable MOF host framework and methyl viologen guest molecule. The π-stacking arrangements adjust the distance between the D–A components, contributing to the formation of an ultra long-lived charge separated state in the photo/thermo dual stimuli-responsive complex.

An air-stable photoresponsive viologen molecular system is constructed based on a three-fold accordion interpenetrating packing arrangement. The fluorescent modulation process is coupled with a photochromic reaction via energy and electron transfer between the adjacent donor and acceptor groups.

A new photochromic coordination network is constructed via the combination of viologen and carboxylate fragments. Close packing of the two-fold diamond-like interwoven mode creates electron transfer bridges for the acceptor and donor components. Radicals are generated upon photoirradiation and are accompanied by a color change from yellow to blue-green.

A new type of metal-phosphate-base cation sensor is constructed via attaching organic TPT fluorophores to the framework of the porous inorganic layers. It shows excellent sensitivity and selectivity for a series of cations.

A new type of photochromic supramolecule is designed and synthesized via the suitable combination of two nonphotoactive organic molecules tpt and btec. The connections built by strong intermolecular forces provide the possibility for contact electron transfer. Reversible color changes of the molecular switch are observed upon exposure to light irradiation.

The replacement of liquid bases by solid base catalysts is a crucial requirement for sustainable industrial processes. The use of heterogeneous catalysts can improve the overall atom catalytic efficiency of reactions and facilitate the organic separation process. Here, we report the synthesis and characterization of a germanium coordination complex Ge(C3H6ONH2)2(OH)2(1). Complex 1 is obtained by hydrothermal synthesis and is crystallized in the monoclinic system, space group P21/c with a = 10.250 (2) Å, b = 9.810 (2) Å, c = 10.360 (2) Å, and β = 100.70 (3)°. Single crystal data indicate that the Ge4 + ion has octahedral coordination geometry surrounded by two 2-hydroxypropylammine molecules. Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate is carried out with compound 1 as solid catalytic support in ethanol at 333 K. Experimental results indicate that it is an efficient base catalyst. The reaction gives a 98% yield for the condensation product.A new solid basic catalyst based on the germanium coordination complex Ge(C3H6ONH2)2(OH)2 is synthesized and characterized. The use of the solid base for Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate gives a high catalytic performance.Highlights► A new germanium coordination complex is synthesized and characterized. ► Its structure is characterized by single crystal data. ► Phase purity of the bulk sample is confirmed by XRPD data. ► The solid base is tested as solid catalytic support in the Knoevenagel condensation. ► It affords high basic catalytic performance.

The photo-response nature of two novel mixed-ligand MOF complexes depends on their framework conformations. It demonstrates for the first time that photochromic material can be produced with the suitable combination of two non-photoactive ligands on a MOF structure.

Two new zincophosphites are obtained via a hydrothermal process. Single crystal data indicate that 1 has a two dimensional motif with the organic amine template embedded between the layers, while 2 has a three-dimensional structure with the organic amine template enclosed into the cavities. Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate is carried out with these two complexes as support in ethanol at 333 K respectively. Experimental results indicate that only 1 is efficient for the catalysis. The catalytic ability depends on their structural characters.Two new zincophosphites are synthesized and characterized. Studies on Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate over them indicate that the catalytic performance of compound 1 is better than that of compound 2.Research Highlights►Two zinc phosphites are used for the catalysis of Knoevenagel condensation reaction. ►Their structures are characterized by single crystal data. ►The catalytic ability depends on their structural characters. ►The catalytic performance of compound 1 is better than that of compound 2.

A new stable mixed-ligand metal organic framework Zn2(tpt)2(2-atp)I21 (tpt = tris (4-pyridyl) triazine, 2-atp = 2-aminoterephthalate) with split channels has been synthesized and characterized. The nitrogen containing ligands tpt and 2-atp are selected to create attractive basic sites for the catalyst. The Knoevenagel condensation between benzaldehyde and the active hydrogen compound (ethyl cyanoacetate or malononitrile) is carried out using compound 1 as solid basic catalytic support. The test results indicate that 1 is an efficient base catalyst with selective catalytic properties. It gives 37% and 99% yield respectively for the condensation products ethyl (E)-α-cyanocinnamate and 2-benzylidenemalononitrile. TG data show that the solid catalyst sample is fairly thermally stable. The compound does not show any signs of decomposition until 420 °C. PXRD data support that the catalyst remains its crystalline and framework stability after the catalysis process. These characters make it easily to be regenerated for the next cycle.A new stable mixed-ligand metal organic framework Zn2(tpt)2(2-atp)I21 with split channels has been synthesized and characterized. It is an efficient catalyst with selective base catalytic properties. The robust framework makes it easily to be regenerated for the next cycle.Highlights► A new stable MOF with split channels has been synthesized and characterized. ► The structure is characterized by single crystal data. ► Purity and stability of the bulk sample are confirmed by TG and XRPD data. ► It is tested as solid catalytic support in the knoevenagel condensation. ► The efficient base catalyst has an interesting size selectivity character.

A new two-dimensional metal organic framework is synthesized and characterized. The encapsulated chloride anions organize a collection of building units into a novel mixed-ligand metal organic supramolecular assembly, indicating specific host–guest recognition. By contrast, the addition of F−, Br−, I−, PO43- anions only give out the coordination complexes with single ligand. Reactions of the Zn2+ ion with 1,2,4-benzenetricarboxylic acid and pyridine-2,5-dicarboxylic acid have been investigated with emphasis on the factors that govern reaction results. And the sample is characterized by the elemental analysis, TGA, XPRD, IR, and luminescent data.A new two-dimensional metal organic framework is synthesized and characterized by single crystal, TGA, XPRD, IR, and luminescent data. The encapsulated chloride anions organize a collection of building units into a novel mixed-ligand metal organic supramolecular assembly, indicating specific host–guest recognition.

A unique hydrothermal selective hydrogenation process is carried out effectively in a simple and friendly way without adding any precious metal catalysts and hydrogen gas from outside. The self-assembly of the hydrogenated product 3-(4-(pyridin-4-yl)piperidin-1-yl) benzoate (PYPDB) with the zinc ion produces a highly stable photoactive complex Zn(PYPDB)2 displaying interesting long range electron transfer behavior in the conjugated ring system.

A new type of metal-phosphate-base cation sensor is constructed via attaching organic TPT fluorophores to the framework of the porous inorganic layers. It shows excellent sensitivity and selectivity for a series of cations.

A new hybrid organic zinc phosphate–phosphite with a tris (4-pyridyl) triazine molecule embedded in the cavity of an extra-large 24-ring channel has been synthesized and characterized. A strong luminescence emission is observed, which is due to the close packed array of organic ligands. The covalent coupling of fluorescent and photochromic components builds a novel phosphate-based photoactive dyad system.

The photo-response nature of two novel mixed-ligand MOF complexes depends on their framework conformations. It demonstrates for the first time that photochromic material can be produced with the suitable combination of two non-photoactive ligands on a MOF structure.

Suitable combination of organic fragments N-(3-carboxyphenyl)-4,4′-bipyridinium and m-benzene dicarboxylate affords a new type photochromic metal–viologen coordination polymer with close packed arrangements. The aggregates build an interesting stable crystalline framework showing long lived color constancy. Repeating cycles of reversible color changes are observed for the molecular switch in air upon photoirradiation.

A dual stimuli-responsive system was constructed by introducing methyl viologen into a luminescent europium–organic framework with a compact packing mode. In addition to absorption and emission properties that are sensitive to both light and heat involving electron/energy transfer processes, the photoactive MOF has a spectral response from UV to the visible region.

Keggin polyphosphotungstate cluster was captured by a porous molecular ring with light sensitizing TPT molecules as connectors and copper ions as nodes. The self-assembly reaction gives a stable host–guest supramolecular system, demonstrating efficient heterogeneous photocatalytic behavior for the degradation of methyl orange in near-neutral conditions.

An air-stable photoresponsive viologen molecular system is constructed based on a three-fold accordion interpenetrating packing arrangement. The fluorescent modulation process is coupled with a photochromic reaction via energy and electron transfer between the adjacent donor and acceptor groups.

A new type of electron transfer (ET) system was built via the combination of a highly stable MOF host framework and methyl viologen guest molecule. The π-stacking arrangements adjust the distance between the D–A components, contributing to the formation of an ultra long-lived charge separated state in the photo/thermo dual stimuli-responsive complex.