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In the present work, we report a "two-in-one" strategy to construct single-linker-based pillar-layered metal–organic frameworks (PL-MOFs) guided by reticular chemistry via an in situ "one-pot" approach. Two carboxyl groups and one pyridine group are integrated into one molecular skeleton to form bifunctional organic linkers via the reaction of pyridine-containing aldehyde and bicarboxylate-containing o-phenylenediamine. During the synthesis of organic linkers, two zinc-based PL-MOFs, non-interpenetrated HIAM-3016-op and two-fold interpenetrated HIAM-3017-op, can be simultaneously constructed. The different interpenetrations for these two PL-MOFs can be attributed to the increased length of the pyridine-containing moiety. HIAM-3017-op can be utilized for Cr2O72− detection with excellent sensitivity and selectivity. The present work not only provides a novel insight to design and prepare PL-MOFs with specific structures guided by reticular chemistry, but also indicates the universality of the in situ "one-pot" strategy to construct porous materials. [ABSTRACT FROM AUTHOR]

A special functional group mediated functionalization platform is introduced as a new and versatile platform tool to improve the fluorescence detection performance of metal–organic frameworks (MOF). The creation of a mixed-functionalization strategy on a MOF realizes the high sensitivity detection of heavy metal ions, anions and small molecules. In this work, we have first reported a novel amino functionalized 3D indium MOF [In(BDC-NH2)(OH)]n (In1-NH2) which not only has an excellent fluorescent characteristic but also shows highly sensitive identification of Fe3+, Cu2+, Pb2+ and ClO− in water with broad linear ranges and short response times. Subsequently, based on the remaining amino group site of In1-NH2, a post-synthetic modification strategy is utilized to introduce an active boronic acid group for hydrogen peroxide detection. The obtained PBA-In1 exhibits an efficient sensing performance for hydrogen peroxide with an LOD of 0.42 μM. Given this, PBA-In1 is expected to become an effective probe to monitor the formation of metabolites in humans. In1-NH2 successfully achieves multiple ion detection and the PBA-In1 sensing platform with boronic acid functionalization may have good application prospects in biochemical research in the future. [ABSTRACT FROM AUTHOR]

Effective and simultaneous organic micropollutant and insoluble oil removal from wastewater by using smart materials and feasible strategies is still a huge challenge. Herein, we design a novel two-dimensional (2D) metal–organic framework (MOF) {[Zn3(bcoba)2(H2O)2]·4DMA·2H2O}n (kgd-Zn) (H3bcoba = (3,5-bis((3′-carboxylbenzyl)oxy)benzoic acid)) with a kgd topology by using a reticular chemistry strategy for highly efficiently removing hazardous substances from wastewater. The excellent ciprofloxacin (CIP) adsorption of kgd-Zn may be attributed to the strong interaction forces between pollution molecules and the MOF. In addition, a macroporous melamine foam (MF) supported hybrid composite kgd-Zn@MF is prepared accordingly. The adsorption performance of CIP is significantly optimized due to the hierarchical microporous–macroporous kgd-Zn@MF system. Moreover, the synergetic hydrophobic/oleophilic properties endow the kgd-Zn@MF composite with an exceptional oil/water separation ability, including a high adsorption capacity (5077–13 786 wt%) towards various solvents and oils, easy collection and remarkable recyclability over 50 cycles. Meanwhile, the hybrid kgd-Zn@MF can simultaneously remove CIP molecules and soybean oil from simulated multi-component wastewater and the removal efficiencies reach above 99.0%, exhibiting a dual functional performance. This work presents a promising strategy of oriented design and topological construction of MOF materials and MOF-based composites acting as excellent candidates for purifying drinking water. [ABSTRACT FROM AUTHOR]

A multifunctional calcium coordination polymer (Ca-CP) formulated as [(CH3)2NH2][Ca(Me2tcpbH)(H2O)] (1) has been synthesized and characterized. Compound 1 features a robust and novel three-dimensional (3D) network with cage-like cavities. The high thermal and moisture stability of the title compound makes it a good candidate for possible environment or energy related applications. Fluorescence (FL) studies demonstrate that 1 shows emission with a maximum at 350 nm under 270 nm excitation. The title compound acts as a selective and sensitive fluorescent sensor for the detection of acetone and Fe3+ ions at low concentrations. The FL intensity quenching percentage and the concentration ratio of Fe3+/Fe2+ showed a linear relation with a Fe3+ concentration as low as 50 μM in Fe2+ aqueous solutions, offering an easy way to probe the extent of Fe2+ oxidation. Moreover, due to the relatively high hydration character of Ca2+, the terminal water molecules and undeprotonated carboxylate groups form a strong hydrogen-bonded network within the structure, facilitating its tunable proton conduction under various humidity and temperature conditions. The proton conducting mechanism has been investigated using PXRD, IR, and EA methods. [ABSTRACT FROM AUTHOR]

A three-dimensional (3D) and highly fluorescent calcium-based coordination polymer (Ca-CP) has been synthesized and structurally characterized. Built on a strongly fluorescent (FL) chromophore ligand, [Ca(H2tcbpe)(H2O)2] (1) (H4tcbpe = 4′,4′′′,4′′′′′,4′′′′′′′-(ethene-1,1,2,2-tetrayl)tetrakis(([1,1′-biphenyl]-4-carboxylic acid))) is highly luminescent. Photoluminescence (PL) studies indicate that 1 undergoes a bathochromic shift in emission energy from blue to green color upon outgassing or under mechanic force. Notably, 1 exhibits selective FL sensing for Cu2+ ions with a detection limit (LOD) of 0.064 ppm, far below the U.S. WHO and EPA standard for drinking water. Detailed investigation of the sensing mechanism reveals that uncoordinated COO− groups in 1 play a major role in recognizing Cu2+ ions. This is supported through analysis by multiple characterization methods including IR, EDS and XPS. Based on the proposed mechanism, an isostructural [Ca(H2tcbpe-F)(H2O)2] Ca-CP (2) (H4tcbpe-F = 4′,4′′′,4′′′′′,4′′′′′′′-(ethene-1,1,2,2-tetrayl)tetrakis(3-fluoro-[1,1′-biphenyl]-4-carboxylic acid)) is synthesized and tested. Compound 2 demonstrates a ten-fold enhancement in Cu2+ detection sensitivity with a ppb level detection limit. The strong enhancement in the detection sensitivity results from optimized electron density around free COO− groups by introducing electron withdrawing F groups onto the backbone of the organic linker. Excellent chemical stability under a wide range of pH conditions (1–14), high sensitivity and rapid fluorescence quenching response time (seconds) make these compounds ideal candidates for use as Cu2+ sensors. [ABSTRACT FROM AUTHOR]

A robust hafnium-based metal organic framework, Hf-PBTA, with sensitive and self-calibrating dual-emissive fluorescence response towards sulfite and sulfonic derivatives, including antibiotic sulfamethazine, has been developed, which shows fast detection of sulfite ions at a concentration as low as 76 ppb. The opposite response tendency from two radiative pathways towards aromatic sulfonic molecules and sulfite anions stems from the synergistic effect of the pyridine protonation effect, π–π stacking interaction and intramolecular twist motion. [ABSTRACT FROM AUTHOR]

The quantum spin Hall effect, the valley Hall effect and ferroelectricity are all extensively studied yet distinct properties of insulators and it would be very interesting to see if they could coexist in certain two-dimensional (2D) materials. We present a family of fluorinated methyl-functionalized bismuthene (Bi2C2H6−xFx) films to achieve the 2D ferroelectric valley topological insulator (FEVTI) state, due to strong spin–orbit coupling (SOC) and non-centrosymmetric layer structures. Bi2C2H6−xFx films have topological non-trivial band gaps up to 1.08 eV, which are robust against the coverage and distribution of fluorine atoms, and the strongest out-of-plane ferroelectric polarization is up to 0.25 × 10−10 C m−1. Moreover, some Bi2C2H6−xFx configurations exhibit an extra valley degree of freedom by the valley splitting at the K and K′ points in the Brillouin zone due to the symmetry breaking, resulting in the coexistence of quantum spin and valley Hall states. These phenomena could also be found in other similarly decorated 2D materials, therefore offering unique quantum material platforms for discovering novel physics and exploring innovative applications. [ABSTRACT FROM AUTHOR]

The most serious and yet unsolved problems of molecular logic operations consist of how to link molecular events in complex systems into a usable device with specific functions. Herein, a fluorescence system based on a Eu(iii)-functionalized Cu(i)-coordination polymer was constructed to recognize and connect multiple components (AA/H2O2, H2S and Fe(ii)) for developing dual-emissive (B485 and R616) ratiometric fluorescent sensing and integrating Boolean logic operations. More importantly, we first proposed the H2O2–Eu(iii)@Cu-COOH system, which can realize the selective and quantitative detection of AA by fluorescence titration experiments of H2O2 even in the presence of various competitive analytes (e.g. H2S and Fe(ii)). To demonstrate the strategy, by self-assembling, oxidizing, and connecting with each other, Eu(iii)@Cu-COOH and the analytes achieved elementary logic operations (OR, NOR, AND, XOR, IMP and INH) and integrative logic operation (XOR(INH)–OR) to perform non-arithmetic functions and to analyze two or three analytes in a bio-mimicking environment. Considering its strong molecular recognition, the novel prototypes developed here may have potential applications in the fields of biological computers and intelligent multi-analytes detection systems. [ABSTRACT FROM AUTHOR]

A large bulk band gap is critical for the application of two-dimensional topological insulators (TIs) in spintronic devices operating at room temperature. On the basis of first-principles calculations, we predict BiXH (X = OH, SH) monolayers as TIs with an extraordinarily large bulk gap of 820 meV for BiOH and 850 meV for BiSH, and propose a tight-binding model considering spin–orbit coupling to describe the electronic properties of BiXH. These large gaps are entirely due to the strong spin–orbit interaction related to the pxy orbitals of the Bi atoms of the honeycomb lattice. The orbital filtering mechanism can be used to understand the topological properties of BiXH. The XH groups simply remove one branch of orbitals (pz of Bi) and reduce the trivial 6-band lattice into a 4-band, which is topologically non-trivial. The topological characteristics of BiXH monolayers are confirmed by nonzero topological invariant Z2 and a single pair of gapless helical edge states in the bulk gap. Owing to these features, the BiXH monolayers of the large-gap TIs are an ideal platform to realize many exotic phenomena and fabricate new quantum devices working at room temperature. [ABSTRACT FROM AUTHOR]

The fabrication of luminescent materials with lanthanide cations encapsulated within MOF pores is currently of interest because luminescent materials are used in numerous applications. In this study, a distinctive strategy via postsynthetic modification (PSM) of a novel metal–organic framework [Cu(HCPOC)2]n (Cu1) (H2CPOC = 5-(4′-carboxyphenoxy)nicotinic acid) and terbium ions (Tb3+) for sensing hydrogen sulfide (H2S) is reported. The obtained composite Tb3+@Cu1 emits a weak typical Tb3+ ion emission and strong ligand-centred emission. Interestingly, H2S, as a strong electron donor, can strongly enhance the luminescence of Tb3+ through its superior affinity for Cu2+ ions. The composite Tb3+@Cu1 was designed as a luminescent turn-on ratiometric probe for H2S detection, showing high sensitivity and selectivity. The detection limit of Tb3+@Cu1 (1.20 μM) is far below that of Cu1 (13.25 μM). Moreover, a similar ligand, 5-(4′-carboxyphenyl)nicotinic acid (H2CPC), was used to synthesize a fascinating structure, [Cu5(CPC)2(HCPC)2(OH−)4]n (Cu2), which was quite similar to that of the famous semiconductor MoS2, with the advantageous support of an organic linker between layers, and it showed a band gap of 2.45 eV. [ABSTRACT FROM AUTHOR]

Three novel metal–organic assemblies (MOAs), namely, [Ag(2,4′-Hpdc)(4,4′-bpy)]n (1), [Ag(2,2′-Hpdc)(4,4′-bpy)0.5]n (2), and [Cu(2,2′-Hpdc)2(1,4-bib)]n (3) [2,4′-H2pdc = 2,4′-biphenyldicarboxylic acid; 2,2′-H2pdc = 2,2′-biphenyldicarboxylic acid; 4,4′-bpy = 4,4′-bipyridine; 1,4-bib = 1,4-bis(1-imidazolyl)benzene] have been hydrothermally synthesized by using mixed ligands and characterized by single crystal X-ray diffraction, infrared (IR), elemental analysis and thermogravimetric analysis (TGA). The crystal structures of the three compounds indicate that the hydrogen bonding (C–H…O and C–H…π) and π…π stacking interactions play critical roles in the formation of an extended supramolecular array. The combination of C–H…π and π…π stacking interactions endow 1 with a 3D network. 2 displays a rare 3D structure with a unique 1D structure based on an eight-membered {Ag2C2O4} ring and compound 3 shows a 1D chain structure, which is propagated to form an extended 3D structure only by C–H…π hydrogen bonding. The two Ag(i)-compounds display blue emissions in the solid state at 298 K and 77 K. More significantly, compound 1 shows excellent selectivity, fast detection time (＜5 min), and high sensitivity (detection limit, 9.63 nM) for Hg2+ ions in aqueous solution due to a great enhancement of 1-luminescence, which can be attributed to Hg2+ cation binding by a non-coordinated carboxyl group efficiently. This is a rare example of Hg2+ detection in aqueous solution based on luminescent silver MOAs. In addition, adsorption spectra reveal the semiconductive nature (2.76 eV for 2, but not detected for 1), thus the role of the Ag…Ag interaction in controlling the performance of the semiconductor properties is highlighted. [ABSTRACT FROM AUTHOR]

Four novel luminescent materials, namely, [Ag3(3,2′,3′-dpob)(bpy)]n (1·Ag), [Ag(3,3′,4′-H2dpob)(bpy)]n (2·Ag), [Ag3(3,2′,3′-Hdpob)(3,2′,3′-H2dpob)(bib)3·2H2O]n (3·Ag), and [Cu(3,2′,3′-Hdpob)(bib)·2H2O]n (4·Cu) [3,2′,3′-H3dpob = 3-(2′,3′-dicarboxylphenoxy)benzonic acid; 3,3′,4′-H3dpob = 3-(3′,4′-dicarboxylphenoxy)benzonic acid; bpy = 4,4′-bipyridine; bib = 1,4-bis(1-imidazoly)benzene] have been hydrothermally synthesized by mixed ligands and characterized using single crystal X-ray diffraction, infrared (IR), elemental analysis and thermogravimetric analysis (TGA). The crystal structures of four compounds indicate that the hydrogen bonding (O–H…O, C–H…O and C–H…π) and π…π stacking interactions play critical roles in the formation of the extended supramolecular array. 1·Ag displays a rare 3D compact structure with a 1D right-handed helical chain [–Ag1–CO2–Ag3–CO2–Ag1–]. 2·Ag and 3·Ag exhibit a 3D supramolecular architecture linked by intermolecular hydrogen bonds based on a 1D double-chain and 1D triple-chain, respectively. 4·Cu shows a 1D + 1D → 2D sheet, which is propagated to form an extended 3D structure with pcu (primitive cubic) topology viaπ…π stacking. The four compounds display remarkable narrow band emission with smaller full width at half-maximum (FWHM) (77 K, 97.91, 92.27, 72.98 and 77.96 nm; 298 K, 169.41, 241.98, 293.66 and 148.50 nm) in the solid state. The combination of such narrow FWHM and the red-shift from 298 K to 77 K endow them with a prominent thermochromic effect. It is worth noting that 2·Ag and 3·Ag display good aggregation-induced emission (AIE) properties. Both of them show very weak luminescence in dimethyl sulfoxide (DMSO, good solvent) while their intensities increased enormously with the addition of water (H2O, poor solvent) due to aggregation. In addition, adsorption spectra reveal their semiconductive nature (2.35 eV for 1·Ag and 2.91 eV for 3·Ag) and the role of Ag…Ag interactions in controlling the performance of semiconductive properties is highlighted. [ABSTRACT FROM AUTHOR]

In this work, a rare 2D → 3D single-crystal-to-single-crystal transformation (SCSC) is observed in metal–organic coordination complexes, which is triggered by thermal treatment. The 2D two-fold interpenetrating square lattice layer [Cd(IBA)2]n (1) is irreversibly converted into a 3D four-fold interpenetrating diamond framework {[Cd(IBA)2(H2O)]·2.5H2O}n (2) (HIBA = 4-(1H-imidazol-1-yl)benzoic acid). Consideration is given to these two complexes with different interpenetrating structures and dimensionality, and their influence on photovoltaic properties are studied. Encouraged by the UV-visible absorption and HOMO–LUMO energy states matched for sensitizing TiO2, the two complexes are employed in combination with N719 in dye-sensitized solar cells (DSSCs) to compensate absorption in the ultraviolet and blue-violet region, offset competitive visible light absorption of I3− and reducing charge the recombination of injected electrons. After co-sensitization with 1 and 2, the device co-sensitized by 1/N719 and 2/N719 to yield overall efficiencies of 7.82% and 8.39%, which are 19.94% and 28.68% higher than that of the device sensitized only by N719 (6.52%). Consequently, high dimensional interpenetrating complexes could serve as excellent co-sensitizers and have application in DSSCs. [ABSTRACT FROM AUTHOR]

Based on a new asymmetric semi-rigid V-shaped tricarboxylate ligand 3-(2′,3′-dicarboxylphenoxy)benzoic acid (H3dpob), a series of zinc/cadmium(ii) coordination polymers, {[Cd(Hdpob)(H2O)3]·H2O}n (1), [Cd(Hdpob)(bib)]n (2), [Zn(Hdpob)(bib)0.5]n (3), {[Cd1.5(dpob)(2,2′-bipy)]·0.5H2O}2n (4) and {[Cd3(dpob)2(4,4′-bipy)2]·3H2O}n (5) [bib = 1,4-bis(1-imidazolyl)benzene; 2,2′-bipy = 2,2′-bipyridine; 4,4′-bipy = 4,4′-bipyridine], have been successfully synthesized via hydro(solvo)thermal reactions. 1 forms a three dimensional (3D) supramolecular structure linked by two types of intermolecular hydrogen bonds based on zig-zag 1D chains, whereas 2 and 3 are obtained with a similar 2D layer structure by the same ligands and further connected into a 3D structure through hydrogen bonds. 4 displays a homochiral 2D structure though two achiral ligands 2,2′-bipy and H3dpob, which contains right-handed helical infinite chains. 5 is a 3D structure containing 2D metal-pyridine layer motifs, which are further pillared by beaded dpob3− ligands to complete the structure and form a 6-connected pcu (primitive cubic) net. In DMSO solvent, 1–5 illustrate dual-emission properties but have different low-energy emission (LE) intensities relatively. Extraordinarily, the difference resulting from central metals between 2 and 3 makes the intensity of LE dramatically enhanced and quenched. In this regard, the luminescence of 2 and 3 can be tuned between blue and green regions by varying the excitation light, and the tuning tendency can be tailored with inverse directions. Comparing their tunable-sensitivity to energy quantitatively, the theoretical calculation displays that 3 (4.29%) is little higher than 2 (3.59%) in a relative lower excitation wavelength zone. Meanwhile, five coordination polymers show distinct luminescence thermochromism in the solid state. When the temperature decreases from 298 K to 77 K, the red-shift from blue/green to the pure yellow light region is highlighted. The fantastic and unique luminescence phenomenon not only brings an insight into the synthesis of dual-emissive materials, but helps us to understand the luminescence behavior deeply as well. [ABSTRACT FROM AUTHOR]

In the present work, we report a "two-in-one" strategy to construct single-linker-based pillar-layered metal-organic frameworks (PL-MOFs) guided by reticular chemistry via an in situ "one-pot" approach. Two carboxyl groups and one pyridine group are integrated into one molecular skeleton to form bifunctional organic linkers via the reaction of pyridine-containing aldehyde and bicarboxylate-containing o -phenylenediamine. During the synthesis of organic linkers, two zinc-based PL-MOFs, non-interpenetrated HIAM-3016-op and two-fold interpenetrated HIAM-3017-op, can be simultaneously constructed. The different interpenetrations for these two PL-MOFs can be attributed to the increased length of the pyridine-containing moiety. HIAM-3017-op can be utilized for Cr 2 O 7 2- detection with excellent sensitivity and selectivity. The present work not only provides a novel insight to design and prepare PL-MOFs with specific structures guided by reticular chemistry, but also indicates the universality of the in situ "one-pot" strategy to construct porous materials.

Luminescent metal-organic frameworks (LMOFs) with diverse structural features and promising fluorescence-based applications have attracted wide attention in the past two decades. In this work, a LMOF with the formula [Ca 4 (tcbpe-F) 2 (H 2 O) 3 ] (1, LMOF-411) has been constructed from calcium (Ca) and 1,1,2,2-tetrakis(4-(4-carboxyphenyl)phenyl)ethene (H 4 tcbpe-F). Compound 1 features a three-dimensional framework with a 10-nodal net topology. Due to the relatively high hydration energy of Ca 2+ , compound 1 readily transforms into a new phase formulated as [Ca(H 2 tcbpe-F)(H 2 O) 2 ] (1') upon exposure to water. Combining experimental characterization and theoretical calculations, we elucidated the mechanism of H 2 O-induced phase transition from 1 to 1'. Notably, the water induced phase transformation can be detected visibly from the change in luminescence, which originates from the fluorescent linker. Compound 1 emits green light ( λ em = 490 nm) under UV excitation, while compound 1' emits bright yellow light ( λ em = 550 nm) under blue excitation (450 nm). Compound 1' represents the first Ca based LMOF yellow phosphor and its luminescence quantum yield reaches 68%. It can be coated directly onto a commercial blue light-emitting-diode (LED) chip to fabricate a white LED (WLED)., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A special functional group mediated functionalization platform is introduced as a new and versatile platform tool to improve the fluorescence detection performance of metal-organic frameworks (MOF). The creation of a mixed-functionalization strategy on a MOF realizes the high sensitivity detection of heavy metal ions, anions and small molecules. In this work, we have first reported a novel amino functionalized 3D indium MOF [In(BDC-NH2)(OH)]n (In1-NH2) which not only has an excellent fluorescent characteristic but also shows highly sensitive identification of Fe3+, Cu2+, Pb2+ and ClO- in water with broad linear ranges and short response times. Subsequently, based on the remaining amino group site of In1-NH2, a post-synthetic modification strategy is utilized to introduce an active boronic acid group for hydrogen peroxide detection. The obtained PBA-In1 exhibits an efficient sensing performance for hydrogen peroxide with an LOD of 0.42 μM. Given this, PBA-In1 is expected to become an effective probe to monitor the formation of metabolites in humans. In1-NH2 successfully achieves multiple ion detection and the PBA-In1 sensing platform with boronic acid functionalization may have good application prospects in biochemical research in the future.

Three novel metal-organic assemblies (MOAs), namely, [Ag(2,4'-Hpdc)(4,4'-bpy)] n (1), [Ag(2,2'-Hpdc)(4,4'-bpy) 0.5 ] n (2), and [Cu(2,2'-Hpdc) 2 (1,4-bib)] n (3) [2,4'-H 2 pdc = 2,4'-biphenyldicarboxylic acid; 2,2'-H 2 pdc = 2,2'-biphenyldicarboxylic acid; 4,4'-bpy = 4,4'-bipyridine; 1,4-bib = 1,4-bis(1-imidazolyl)benzene] have been hydrothermally synthesized by using mixed ligands and characterized by single crystal X-ray diffraction, infrared (IR), elemental analysis and thermogravimetric analysis (TGA). The crystal structures of the three compounds indicate that the hydrogen bonding (C-HO and C-Hπ) and ππ stacking interactions play critical roles in the formation of an extended supramolecular array. The combination of C-Hπ and ππ stacking interactions endow 1 with a 3D network. 2 displays a rare 3D structure with a unique 1D structure based on an eight-membered {Ag 2 C 2 O 4 } ring and compound 3 shows a 1D chain structure, which is propagated to form an extended 3D structure only by C-Hπ hydrogen bonding. The two Ag(i)-compounds display blue emissions in the solid state at 298 K and 77 K. More significantly, compound 1 shows excellent selectivity, fast detection time (<5 min), and high sensitivity (detection limit, 9.63 nM) for Hg 2+ ions in aqueous solution due to a great enhancement of 1-luminescence, which can be attributed to Hg 2+ cation binding by a non-coordinated carboxyl group efficiently. This is a rare example of Hg 2+ detection in aqueous solution based on luminescent silver MOAs. In addition, adsorption spectra reveal the semiconductive nature (2.76 eV for 2, but not detected for 1), thus the role of the AgAg interaction in controlling the performance of the semiconductor properties is highlighted.