Pillared-layer Framework Research Articles

Tetragonal multilayered ZnO/CuO composites derived from Zn- and Cu-containing metal-organic framework: Effect of calcination temperature on physicochemical properties and photocatalytic activity

Tetragonal multilayered ZnO/CuO composites prepared by the annealing of a Zn- and Cu-containing pillar-layered metal-organic framework were characterized by using instrumental techniques and investigated as catalysts for the degradation of 4-nitrophenol (4-NP) under irradiation with UV–vis light. The as synthesized samples contained p-n junctions, amorphous-crystalline heterojunctions, which benefitted light absorption and charge separation. The calcination temperature significantly influenced both the physicochemical properties and photocatalytic activities of these composites. The sample obtained at 400 °C (TL-ZC-400) exhibited the best photocatalytic performance, achieving a 4-NP degradation efficiency of 93.93% after 40 min of illumination. The TL-ZC-400 still showed high photodegradation ability (97.2%) after four times recycling. Furthermore, the recombination of ZnO and CuO adjusted the band gap structure of TL-ZC-400. Radical trapping experiments showed that the degradation of 4-NP was mainly mediated by hydroxyl radicals and holes. A possible photocatalytic mechanism was also proposed in this study.

Constructing [Co6(μ3-OH)6]-based pillar-layered MOF with open metal sites via steric-hindrance effect on ligand for CO2 adsorption and fixation

With excellent structural tunability and well framework stability, pillar-layered metal-organic frameworks (PL-MOFs) are promising candidates as sorbents and catalysts. Yet, the open metal sites (OMSs) in PL-MOFs are usually fully occupied by the pillar ligands, mostly limiting their involvement in CO2 adsorption and fixation. Herein, in consideration of the 12-connected [Co6(μ3-OH)6]-based PL-MOFs (Co6-MOF-3), a strategy based on steric-hindrance effect on pillar linker is proposed to create OMSs on their metal cluster nodes. The 4,4′-(9,10-anthracenediyl)bis-Pyridine (ABPY) that possessed anthracene groups was selected as the pillar linker, and a new [Co6(μ3-OH)6]-based PL-MOF (DZU-6) with accessible open Co(ii) sites was successfully synthesized. Single crystal structure of DZU-6 analysis reveals that ABPY ligands which were firstly linked to the metal clusters prevented the other ABPY ligands from coordinating with the nodes due to the steric-hindrance effect on ligands, resulting that four sites on [Co6(μ3-OH)6] were occupied by the terminal solvent molecules. The coordinated solvent molecules in DZU-6 could be removed easily, meanwhile the porosity was preserved (BET surface 2566 m2 g−1). Importantly, CO2 adsorption and catalytic cycloaddition conversion of DZU-6 were performed that the CO2 uptake improved 40% and the catalytic conversion yield increased over 50% compared with isostructural Co6-MOF-3 without OMSs.

Two Bi-MOFs with pyridylmulticarboxylate ligands showing distinct crystal structures and phosphorescence properties

Two Bi-MOFs, [Bi(PDC)(OH)] (Bi-PDC; H2PDC ​= ​2,4-pyridine bicarboxylic acid) and [Bi(PTC)(H2O)2] (Bi-PTC; H3PTC ​= ​2,4,6-pyridine tricarboxylic acid), have been synthesized under almost the same solvothermal condition, respectively. Both Bi-PDC and Bi-PTC were characterized by microanalysis, infrared spectra (IR), thermal gravimetric analyses (TGA), and powder X-ray diffraction (PXRD) techniques. Single-crystal structural analyses indicate that the Bi3+ ions adopt similar coordination sphere of monocapped square antiprism in Bi-PDC and Bi-PTC, while PDC2− and PTC3− ligands display distinct bridging modes through carboxylates and pyridyl groups, leading to Bi-PDC forming three-dimensional (3D) pillared-layer framework and Bi-PTC developing into two-dimensional (2D) layered structure. Two Bi-MOFs emit ligand-centered room temperature phosphorescence due to the heavy atom effect of Bi3+ ion, with lifetime and quantum yield of 0.39 ​ms and 2.49% in Bi-PDC versus 0.57 ​ms and 5.45% in Bi-PTC, and the intense green and orange phosphorescence is visible by naked eyes under ambient condition, and the long-wavelength (orange) phosphorescence Bi-based MOF is seldom reported.

Structure modulation, selective dye adsorption and catalytic CO2 transformation of four pillared-layer metal-organic frameworks

In this paper, a series of metal-organic frameworks (MOFs), namely, [Co(pip)(4,4′-bpy)]n (1), [Co2(pip)2(bibp)]n (2), [Mn(pip)bidmp]n (3) and [Ni(pip)(bibp)(H2O)]n (4) (bpy ​= ​4,4′-bipyridine, bibp ​= ​4,4-bis(imidazolyl)biphenyl, bidmb ​= ​1,4-bis(1-imidazoly)-2,5-dimethylbenzene), have been solvothermally synthesized based on the main ligand 6-(3-pyridyl)isophthalic acid (H2pip) and structurally characterized by various methods. These MOFs all present three dimensional (3D) pillared-layer frameworks, and through systematic modulation of auxiliary ligands and metal ions, their structures can be well regulated from nonporous to porous. Considering their excellent thermal and water stability, the dye removal properties from water solutions of these MOFs were further studied, and notably, 2 which has the largest porosity of the four MOFs, exhibits very fast selective adsorption of methyl orange over Rhodamine B (MO/RhB) with a total MO uptake amount of 83.4 ​mg ​g−1. Moreover, the catalytic CO2 transformation properties of these MOFs were also carried out under mild conditions, of which 2 exhibited the highest catalytic activity with 69.57% yield for propylene carbonate and 50.55% for butylene carbonate, respectively.

A new three-dimensional cadmium(II) coordination polymer based on bis[4-(2-methylimidazol-1-yl)phenyl]methanone: synthesis, structure and properties.

A novel three-dimensional CdII coordination polymer, namely, poly[[(μ3-benzene-1,4-diacetato)(μ2-benzene-1,4-diacetato)bis{μ2-bis[4-(2-methylimidazol-1-yl)phenyl]methanone}dicadmium(II)] tetartohydrate], {[Cd(C10H8O4)(C21H18N4O)]·0.25H2O}n or {[Cd(PBEA)(MIPMO)]·0.25H2O}n, (I), was synthesized by the hydrothermal method using benzene-1,4-diacetic acid (H2PBEA), bis[4-(2-methylimidazol-1-yl)phenyl]methanone (MIPMO) and Cd(NO3)2·6H2O. The title compound was structurally characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy and thermogravimetric analysis, and exhibits a three-dimensional pillar-layer framework based on CdII-PBEA layers and MIPMO pillars, which can be simplified into a pcu topological network. The title compound displays a highly selective and sensitive sensing for Fe3+ ions in aqueous solution. In addition, it displays a high photocatalytic activity for the degradation of methylene blue (MB) in water under UV light irradiation.

Multi-Responsive Luminescent Sensitivities of Two Amide-Decorated Pillared-Layer Frameworks Towards Nitroaromatics, Cr2o72−, Mno4−, and Po43− Anions Based on Diverse Sensing Mechanism

Multi-Responsive Luminescent Sensitivities of Two Amide-Decorated Pillared-Layer Frameworks Towards Nitroaromatics, Cr2o72−, Mno4−, and Po43− Anions Based on Diverse Sensing Mechanism

Inverse CO2/C2H2 separation in a pillared-layer framework featuring a chlorine-modified channel by quadrupole-moment sieving

• A MOF with plentiful Cl atoms hanging on the pore surface was successfully built. • The inverse CO 2 /C 2 H 2 separation was achieved by inserting Cl atoms in the MOF. • Impact of Cl atoms toward adsorb CO 2 and C 2 H 2 is evidenced by simulations. Selective isolation of CO 2 from C 2 H 2 using CO 2 -selective adsorbent is a huge challenge due to their analogous physical properties as well as molecular sizes and shapes. In this work, utilizing an effective strategy of embedding electronegative Cl atoms in pore surface of MOF, a 3D pillared-layer ultramicroporous MOF, [Zn(atz)(BDC-Cl4) 0.5 ] n (1) (Hatz = 3-amino-1,2,4-triazole; BDC-Cl4 = tetrachloroterephthalic acid) for inverse CO 2 /C 2 H 2 separation was successfully constructed. This MOF show a CO 2 /C 2 H 2 (V:V = 1:1) adsorption selectivity of 2.4 at 285 K and 100 kPa. Computational studies further uncover CO 2 recognition mechanism is due to the matching of the unique pore environment decorating by Cl atoms with quadrupole moment of CO 2 .

Solvent mediated photoluminescence responses over mixed-linker cadmium (II) based metal–organic frameworks

Three dimensional mixed-linker cadmium based metal–organic framework (MOF), [Cd2(L1)2(L2)0.5(H2O)]n(1) and {[Cd3(L1a)2(L2)2]⋅H2O}n (2) (L1 = pyrazole-3,5 dicarboxylate, L1a = pyrazolate-3,5 dicarboxylate and L2 = 4,4′-azopyridine) have been synthesized by solvothermal methods. Notably, subtle change in reaction conditions afforded two strikingly different MOFs. Compounds have been characterized structurally by single-crystal X-ray analysis. Both the compounds feature a pillared-layer framework structure. Photoluminescence properties of the framework compounds have been investigated in the solid state as well as in solvent dispersed medium. Interestingly, solvent specific turn-on/turn-off photo-luminescence responses have been observed for both the compounds (1) and (2).

Two unusual metal-organic frameworks based on W/S/Cu clusters and Tetrakis(4-pyridyl)benzene: Enhanced nonlinear optics and efficient luminescence sensing

Tetradentate organic ligand 1,2,4,5-tetrakis (4-pyridyl)benzene (tpb) is firstly developed to build cluster-containing metal-organic frameworks (C-MOFs). Two unusual W/S/Cu C-MOFs {[WS4Cu4I2(TPB)]·DMF}n (1) and {[WS4Cu3Cl(TPB)]·2DMF}n (2) have been synthesized and structurally characterized. 1 is fabricated by 8-connected pentanuclear planar open-shaped cluster [WS4Cu4]2+, 4-connected tetrakis-pyridine TPB unit and I− bridge to form a three-dimensional (3-D) pillar-layered framework. Its (4,8)-connected topology firstly appears in W(Mo)/S/Cu C-MOFs. 2 is constructed by 4-connected T-shaped cluster [WS4Cu3]+, 4-connected TPB unit and terminal Cl− ligand, and possesses a 2-D wave-like (4,4) network. Z-scan experiment reveals that 1–2 have third-order nonlinear optical (NLO) properties. Particularly, 1 exhibits significantly enhanced NLO performance. Moreover, 2 displays strong luminescence, highly sensitive and selective sensing of 2,4,6-trinitrophenol (TNP) in aqueous medium. The efficient emission quenching mechanism of 2 towards TNP is studied as well.

Pore functionalization, single-crystal transformation and selective CO2 adsorption in chemical stable pillared-layer Co(II) based metal–organic framework

The high-efficiency CO2 separation using metal–organic frameworks (MOFs) is crucial in CO2 capture and subsequent conversion for green carbon cycling, yet challenged by rational optimizing the size, shape, sorption site and microenvironment of the pores. The new MOFs with formula [Co2(btd)2(dpbt)2]·3DMF (1) is constructed from two matched long linkers of 4,4′-(benzoic[i1,2,5]thiadiazole-4,7-diyl)dibenzoic (H2btd) and 4,7-di(4-pyridyl)-2,1,3- benzothiadiazole) (dpbt) under solvothermal condition. The compound processes 3-fold interpenetrated pillared-layer frameworks, generating 1D channels sized at 10.8 × 8.2 Å2 and with exposed thiadiazole groups for improved CO2 sorption. The framework is quite rigid confirmed by quite limited changes in crystallographic parameters during solvent exchange and guest removal in single-crystal-to-single-crystal (SC-SC) fashion. The Co(II)-MOF exhibits unprecedented good chemical stability in aqueous solution with pH ranging from 1 to 12, retaining unchanged PXRD patterns for more than 24 h. The activated MOFs show better adsorption for CO2 over N2 with selectivity of 18.8 at 273 K, benefitted from the merits of narrow 1D channels and appending Lewis basic sites on the pore surface.

A two-fold interpenetration pillar-layered metal-organic frameworks based on BODIPY for chemo-photodynamic therapy

The combination of chemotherapy and photodynamic therapy has been proved to be a promising therapy for drug-resistant cancers. In this study, we report, for the first time, a novel two-fold interpenetration pillar-layered metal-organic frameworks (MOFs) material, using BODIPY-derivate bipyridine as linker and Photosensitizer (PS), named BBP-MOFs, was successfully synthesized to serve as a drug carrier and Photodynamic agent simultaneously. The BBP-MOFs could generate singlet oxygen (1O2) to perform PDT under 660 nm light irradiation, in the meantime, the anticancer drugs doxorubicin (DOX) could be loaded for chemotherapy. The results showed that BBP-MOFs exhibited a high drug loading content of 49.7% a controlled drug release and ideal biocompatibility. This DOX loaded BBP-MOFs was readily taken up by HeLa cells, and high levels of 1O2 were generated under light irradiation. This work provided strong evidence for BBP-MOFs as a promising new anticancer drug carrier and PDT candidate, the PDT and chemotherapy combined synergistic therapy revealed high therapeutic efficacy for cancer cells.

Insight understanding into influence of binding mode of carboxylate with metal ion on ligand-centered luminescence properties in Pb-based coordination polymers

In the crystal engineering area, it is important to clearly demonstrating the relationship of structure and certain functionality. Herein, we present the study of the relationship of structure with phosphorescent nature for two new room temperature phosphorescence (RTP) coordination polymers (CPs). [Pb(FDA)(H2O)] (1) and [NH3(CH3)NH2(CH3)2][Pb4(FDA)5] (2), where H2FDA is 2,5-furandicarboxylic acid, have been synthesized by solvothermal method using different solvents and Pb2+ sources and characterized by microanalysis, powder X-ray diffraction (PXRD), thermogravimetric (TG), IR and UV–vis spectra. The Pb2+ ions adopt bicapped triangle prism coordination sphere in 1 and 2, which are connected together via FDA2− ligands into bilayer structure in 1 while pillared-layer framework in 2. The FDA2− ligands show different bridging modes in 1 and 2, leading to distinct coordination interactions between Pb2+ ion and FDA2− ligand in both CPs. Both 1 and 2 emit ligand-centered RTP due to the heavy atom of Pb2+ ion, with a lifetime and quantum yield of 0.62 ms and 14.9% in 1versus 1.69 ms and 15.7% in 2. The emission peak shows significant redshift (79 nm) in 2 regarding 1, which arises from their distinction of coordination interactions between Pb2+ ion and FDA2− ligand in both CPs.

A pillar-layered chalcogenide framework assembled by [Mn5S12N12]n layers and [Sb2S5] inorganic pillars.

Reported here is an attractive pillar-layered metal chalcogenide open framework, in which [Sb2S5] building units act as pillars between [Mn5S12(N2H4)6]n layers. The obtained compound exhibits high stability in both acid and base media and good performance in the electrocatalytic oxygen reduction reaction (ORR).

Efficient detection of Fe(iii) and chromate ions in water using two robust lanthanide metal–organic frameworks

Two novel robust Ln-MOFs feature a 3D highly porous pillared-layer framework and demonstrate selective sensing of Fe(iii) and chromate ions in aqueous solution.

A pillar-layered metal-organic framework based on pinwheel trinuclear zinc-carboxylate clusters; synthesis and characterization

A novel metal-organic frameworks (MOF), namely ({[Zn3(2,6-NDC)3(dabco)]·6DMF·3H2O} (TMU-13) was synthesized by the reaction of 2,6-naphthalenedicarboxylic acid (2,6-NDC) as the O-donor ligand, 1,4-diazabicyclo [2.2.2] octane (dabco) as the N-donor ligand and Zn(II) nitrate hexahydrate. Single crystal X-ray analysis revealed that TMU-13 exhibited a 3D pillar-layered structure based on pinwheel trinuclear zinc-carboxylate clusters as secondary building unit (SBU) with bcu topology and pore window of 12.7 Å × 5.6 Å. Calcination of the compounds TMU-13 at 500 °C under air atmosphere yield ZnO compound.

Three new copper(II) coordination polymers constructed from isomeric sulfo-functionalized phthalate tectonics: Synthesis, crystal structure, photocatalytic and proton conduction properties

Three new copper(II)-based coordination polymers, namely [Cu5(μ3-OH)4 (STP)2(4,4’-bipy)2(H2O)2]·4H2O (CTGU-20), [Cu2(μ2-OH)(SIP)(1,4′-bib)2] (CTGU-21) and [Cu2 (SIP)(4,4′-bibp)2(HCOO)]·3H2O(CTGU-22), (STP ​= ​2-sulfoterephthalate, SIP ​= ​5-sulfoisophthalate, 4,4’-bipy ​= ​4,4’-bipyridine, 4,4′-bibp ​= ​4,4’-bis(imidazolyl)biphenyl and 1,4′-bib ​= ​1,4-bis(1-imidazoly) benzene) have been prepared by two less-developed isomeric sulfo-functionalized phthalate ligands under solvothermal conditions and characterized by PXRD, single crystal X-ray diffraction analysis and thermogravimetric analysis.CTGU-20 exhibits a 3D pillared-layer framework constructed from a unique 1D Cu4O8–CuO4 rod packing unit generated by four μ3-OH groups and pyridyl/carboxylicate mixed linkers. While, CTGU-21 shows a 3D pillared-layer framework extended by Cu2(μ2-OH)(SIP) layers and 1,4′-bib pillars. When 1,4′-bib was replaced by longer 4,4′-bibp, CTGU-22 is obtained, which features a 2D bilayer structure bridged by double 4,4′-bibp ligand. Remarkably, complexes CTGU-20, CTGU-21 and CTGU-22 show promising photocatalytic activities toward the degradation of Rhodamine B(RhB), methyl blue(MB) and 9,10-bis (phenylethynyl)anthracene(BPEA). Moreover, the proton conductivity for three complexes were also studied.

Photocatalytic hydrogen evolution activity over Pt-assisted metal-organic frameworks dominated by transition metal ions and local coordination environments

Three isostructural pillared-layer frameworks with M-BDC-X layers supported by ditopic HL connectors, [M(HL)(BDC)0.5X] n (HL = 4′-(4-hydroxyphenyl)-4,2′:6′,4″-terpyridine, BDC = terephthalate, M = Cd, X = Cl for (1), M = Cd, X = formate for (2), and M = Co, X = formate for (3)), were solvothermally synthesized, and used as photocatalysts for Pt-assisted visible-light-initiated hydrogen evolution from water splitting. These water-durable frameworks exhibit varied hydrogen production rates of 361.2, 271.3, and 327.5 μmol · g−1 · h−1 in 12 h due to their slightly different donor environments of the octahedral CdII and CoII ions. Further experimental and theoretical investigations reveal that the metal ions and the local coordination surroundings have essentially dominated the conduction band minimum and electric resistance of the charge transport, which play highly important roles for the improved catalytic hydrogen evolution ability. These findings demonstrate the electronic effect of the slightly ligand field modifications on the boosting hydrogen generation activity in the noble metal-assisted MOF photocatalytic systems.

Pristine Co(BDC)TED0.5 a pillared-layer biligand cobalt based metal organic framework as improved anode material for lithium-ion batteries

Pillared-layer framework MOFs are considered to be energetic for enhanced performance for anode materials because of rich space and channels for lithium insertion and extraction. We selected pillared-layer MOF, Co(BDC)TED0.5, consisting of an aromatic organic ligand (Terephthalic acid: 1,4-H2BDC) and pillar ligand (Triethylenediamine: TED), synthesized via facile hydrothermal approach and investigated as anode material for LIBs. The time-dependent reaction kinetics of this MOF were investigated to optimize MOF as anode material. The Co(BDC)TED0.5@24h exhibits good rate capability (614 and 239 mAh g−1 at 0.2 and 2.0 A g−1, respectively) with excellent cyclic stability, which is up to 808.2 mAh g−1 after 1000 charge/discharge cycles at 1.0 A g−1 current density. Such an impressive lithium performance is mainly due to channels provided by a pillared-layer framework which not only provides the space for insertion/extraction of Li+ ions but also mitigates the volume expansion during the cycles. The electrochemical process of Co(BDC)TED0.5@24h electrode is elucidated by in-depth series of ex-situ XRD, FTIR, and XPS studies at different charge/discharge states which anticipates the intercalation as working mechanism for Co(BDC)TED0.5. The DFT calculation is also utilized to further confirm the potential binding sites responsible for electrochemical behavior of Co(BDC)TED0.5 as anode materials for LIBs.

Semi-conductive chiral Co-CPs with helixes based on lactic acid derivatives: Synthesis, structures and photocatalyic properties

Among various chiral compounds, semirigid lactic acid derivatives modified from lactic acids have been attractive synthons for the synthesis of chiral coordination polyers (CPs). Herein, lactic acid derivative (R)-4-(1-carboxyethoxy) benzoic acid ((R)-H2CBA) was used to reacted with Co(Ⅱ) ions and auxiliary ligands to obtain two chiral CPs, namely [Co2((R)-CBA)2(2,5-DIP)2]n (1, 2,5-DIP ​= ​2,5-bis(2-methyl-1H-imidazole-1-yl)pyridine) and [Co((R)-CBA)(1,3-DIB) 1.5]n (2, 1,3-DIB ​= ​1,3-di(1H-imidazole-1-yl)benzene). Although two complexes were synthesized under the similar condition, their structural motifs are still very different. Complex 1 has pillared-layer framework with 6-connected mab net and two types of helixes, while complex 2 is 3D supra molecule framework packed by 2D helical layers. UV/vis spectra, Mott-Schottky measurements and electrochemical impedance spectroscopy revealed complexes 1 and 2 are typical n-type semiconductors with low resistance in charge transportation and high charge-separation efficiency. Under UV irradiation, complexes 1 and 2 showed good photocatalytic activity in the degradation of methylene blue. The photocatalytic experiments confirmed that the conversion of MB was up to 88% for 1 and 73% for 2 after 3 ​h, respectively.

3D semiconducting Co-MOFs based on 5-(hydroxymethyl)isophthalic acid and imidazole derivatives: syntheses and crystal structures.

Two three-dimensional cobalt-based metal-organic frameworks with 5-(hydroxymethyl)isophthalic acid (H2HIPA), namely poly[[μ2-1,4-bis(2-methyl-1H-imidazol-1-yl)benzene-κ2N3:N3'][μ2-5-(hydroxymethyl)isophthalato-κ2O1:O3]cobalt(II)], [Co(C9H6O5)(C14H14N4)]n (1), and poly[tris[μ2-1,4-bis(1H-imidazol-1-yl)benzene-κ2N3:N3']bis[μ3-5-(hydroxymethyl)isophthalato-κ2O1:O3:O5]dicobalt(II)], [Co2(C9H6O5)2(C12H10N4)3]n (2), were synthesized under similar hydrothermal conditions. Single-crystal X-ray diffraction analyses revealed that 5-(hydroxymethyl)isophthalate (HIPA2-) and 1,4-bis(2-methyl-1H-imidazol-1-yl)benzene (1,4-BMIB) are simple linkers connecting cobalt centres to build a fourfold interpenetration dia framework in complex 1. However, complex 2 is a pillared-layer framework with a (3,6)-connected network constructed by 1,4-bis(1H-imidazol-1-yl)benzene (1,4-DIB) linkers, 3-connected HIPA2- ligands and 6-connected CoII centres. The above significant structural differences can be ascribed to the introduction of the different auxiliary N-donor ligands. Moreover, UV-Vis spectroscopy and Mott-Schottky measurements confirmed that complexes 1 and 2 are typical n-type semiconductors.