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The first CB[6]-based 3D porous metal-organic rotaxane framework is constructed by the reaction of CuCl2, terephthalic (H2BDC) and CB[6]-based [2]pseudorotaxanes ([PR44]2+·2[PF6]-) under solvothermal conditions. The structure of MORF-1 is a pillared-layer structure with 5-connected sqp topology, in which the effective free volume is 45.4% of the crystal volume. The guest molecules exchange in a single-crystal-to-single-crystal fashion, which was investigated using NMR spectroscopy and X-ray crystallography.

The introduction of halogen atoms into the skeleton to regulate the intrinsic properties or improve task-specific performance of metal–organic frameworks (MOFs) has developed rapidly in recent years. Herein, a series of halogen-engineered MOFs were designed and prepared for electrochemical glucose sensing. Three isomorphic Ni-MOFs were constructed by using tetra-halogenated-phthalic acids as the organic ligand and incorporating 4,4′-bipyridine as an auxiliary ligand. Halogen atoms can enhance the stability of Ni-MOFs through their hydrophobicity and interlayer halogen bonds (X–X or X–π, X = F, Cl, Br). Combined experimental and theoretical results show that the hydrogen bond between halogen atoms and glucose improves the reaction thermodynamics, enabling the wide linear range of 0.01–5.0 mM, high sensitivity of 4709.9 μA mM−1 cm−2 and low detection limit of 0.043 μM. This work provides practical guidance for the rational design of halogenated MOFs and promotes their applications in electrochemical sensing. [ABSTRACT FROM AUTHOR]

Recently, the detection of amino acids has attracted considerable attention in the field of nutrition analysis, health monitoring, and medical diagnosis due to their significance for organisms. In this work, two novel Cd(II)-based metal–organic frameworks (MOFs) with the formulas [Cd(bib)2(SiF6)]n (1) and {[Cd(bib)2(SiF6)]·DMF·3H2O}n (2, bib = 1-(4-imidazol-1-ylphenyl)imidazole) were synthesized and exhibited fluorescence sensing capacity for arginine. In spite of having the same framework composition, complexes 1 and 2 showed great differences in their structure originating in the variations between the coordination modes of SiF62− with Cd2+ and the extension direction of the Cd-bib coordination complexes. Structural analysis manifested that complex 1 featured a 3D coordination framework constructed from 2D Cd-bib coordination layers bridged by SiF62− anions, while complex 2 possessed 3-fold interpenetrated Cd-bib coordination networks connected by SiF62− anions. Furthermore, fluorescence sensing experiments exhibited that both complexes 1 and 2 could be used as fluorescence probes for arginine and the emission intensities of complexes 1 and 2 could be enhanced up to 10.3 and 12.0 times that of the initial emission intensities upon the addition of Arg, respectively. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) as types of proton conductive materials have attracted much attention. Here, an acylamide-functionalized 3D MOF, [Ni3(TPBTC)2(stp)2(H2O)4]·2DMA·32H2O, has been successfully constructed via combining Ni(NO3)2, TPBTC (TPBTC = benzene-1,3,5-tricarboxylic acid tris-pyridin-4-ylamide) and 2-H2stp (2-H2stp = 2-sulfoterephthalic acid monosodium salt) under solvothermal conditions. Single-crystal X-ray diffraction revealed that there are uncoordinated guest DMA molecules in the pores of the compound. On removal of guest DMA molecules, the proton conductivity of the compound increased to 2.25 × 10−3 S cm−1 at 80 °C and 98% RH which is about 110 times that of the original material. It is hoped that this work can provide essential insight for designing and obtaining improved crystalline-state proton conducting materials by considering the influences of guest molecules on proton conduction properties of porous materials. [ABSTRACT FROM AUTHOR]

Two new transition metal–organic frameworks (MOFs) formulated as [Zn3(Bip)3(H2sip)2(H2O)4]·5H2O (CUST-751) and [Cd3(Bip)2(H2sip)2(H2O)4]·2H2O (CUST-752) [CUST = Changchun University of Science and Technology, Bip = 3,5-bis(imidazole-1-yl)pyridine and H2sip = 5-sulfoisophthalic acid monosodium salt] have been constructed via a solvothermal reaction. Their crystal structures have been characterized by single crystal X-ray diffraction. CUST-751 exhibits a two-dimensional (2D) layered structure, while CUST-752 possesses a three-dimensional (3D) framework. Thermogravimetric analysis (TGA) and powder X-ray diffraction (PXRD) after treatment at different temperatures and different relative humidities (RHs) verified that they both have good thermal stabilities and water stabilities. Besides, their utility as fluorescence sensors has also been investigated. The results indicated that both CUST-751 and CUST-752 can be used as multiresponsive fluorescence sensors to detect Fe3+ and Cr2O72− with good sensitivity, high selectivity and recoverability, even in the presence of other interfering ions. More interestingly, CUST-751 is capable of selectively detecting 2,4,6-trinitrophenol (TNP). This work provides insights into the design and synthesis of transition metal based MOFs and explores their potential applications in the fluorescence sensing field. [ABSTRACT FROM AUTHOR]

Three new cucurbit[6]uril (CB[6])-based metal–organic rotaxane networks (MORNs) (named CUST-711, CUST-712, and CUST-713) functionalized by a sulfonic group (–SO3H) have been designed and synthesized via a hydrothermal method. All three compounds exhibited similar two-dimensional (2D) wave layer structures. Their stability under different temperature and relative humidity conditions has been investigated and all the compounds showed excellent stability. Furthermore, their proton conduction properties were also discussed in detail. Due to different structures and sulfonic group sites, the three compounds exhibited different proton conduction abilities of which CUST-712 exhibited an intrinsic relatively high proton conductivity (1.75 × 10−4 S cm−1 at 85 °C and 97% relative humidity). These results provide ideas for the design and synthesis of functional CB[6]-based metal–organic rotaxane frameworks (MORFs) as proton conducting materials. [ABSTRACT FROM AUTHOR]

The selective adsorption/separation of C2 hydrocarbons has been realized in a "flexible-robust" MOF, Zn2(Atz)2Ox. Owing to the distinctive guest-dependent multistep adsorption behaviors and suitable guest–framework interactions, this MOF shows outstanding separation performance for C2H2/C2H4 mixtures in a wide range of temperature confirmed by a column breakthrough experiment. [ABSTRACT FROM AUTHOR]

Three new high-dimensional cucurbit[6]-based metal–organic rotaxane frameworks [Co2(PR43)(BDC)2Cl2]·4H2O (1), [Co2(PR43)(BTC)2]·6H2O (2) and [Co2(PR43)(BPT)2]·20H2O (3) were obtained via the hydrothermal synthesis method. Compound 1 comprised a two-dimensional layered structure, while compounds 2 and 3 exhibited three-dimensional pillared structures. All the compounds showed good thermal stabilities. Furthermore, the magnetic properties of compounds 1–3 were also investigated in detail. [ABSTRACT FROM AUTHOR]

The formation of metal–organic frameworks (MOFs) under given reaction conditions depends on various factors including reaction duration, temperature, used solvent, system pH, and others. Among them, the reaction duration is relatively less investigated. In this work, based on a Cu(ii)-MOF system, the reaction duration was found to play an important role in directing the formation of two different products, (NH2(CH3)2)[Cu12(DDPN)6(H2O)10Cl] (BUT-301) on shorter reaction time and (NH2(CH3)2)2[Cu(DDPN)] (BUT-302) on longer reaction time, when CuCl2 reacted with 3,5-di(3,5-dicarboxylphenyl)nitrobenzene (H4DDPN) in a DMA/MeOH mixed solvent at 120 °C. With increasing the reaction duration, BUT-301 can transform into BUT-302. Both MOFs have three-dimensional (3D) framework structures. BUT-301 is constructed from paddle-wheel Cu2(COO)4 units and DDPN4– ligands as four-connected linkers, while BUT-302 is assembled from mononuclear Cu(ii) centers connecting the ligands as also four-connected linkers but in a monodentate coordination fashion. N2 adsorption confirmed that both MOFs are porous materials with the Brunauer–Emmett–Teller (BET) surface areas of 1953 and 561 m2 g−1, respectively. Interestingly, both BUT-301 and -302 show selective adsorption properties of C3H4 over C3H6. The C3H4/C3H6 adsorption selectivities were calculated to be 1.9 and 4.4 at 0.1 bar and 298 K by the ideal adsorbed solution theory (IAST) for a 1 : 99 C3H4/C3H6 mixture, respectively. [ABSTRACT FROM AUTHOR]

In the design and construction of metal–organic frameworks (MOFs), the utilization of slim ligands is usually more inclined to form interpenetrated structures compared with bulky ones. The structural interpenetration can improve the framework stability and in some cases, enhance gas adsorption capacity and selectivity due to confined pores. In order to explore the structural control of MOFs and construct new MOFs with good selective gas adsorption ability, herein, a slim ethynyl-based 4-connected carboxylate acid ligand, 4,4′,4′′,4′′′-(benzene-1,2,4,5-tetrayltetrakis(ethyne-2,1-diyl))tetrabenzoic acid (H4BTEB), was used to design and construct MOFs, hopefully having interpenetrated structures. Combining with 4-connected paddle-wheel Cu2(COO)4 and 8-connected Zr6O4(OH)8(COO)8 clusters, BTEB4− ligand led to two new MOFs, [Cu2(BTEB)(H2O)2] (BUT-43) and [Zr6O4(OH)8(H2O)4(BTEB)2] (BUT-44). As expected, the two MOFs have two-fold interpenetrated framework structures with partitioned channels. BUT-43 contains a rare three-dimensional (3D) 4-connected single network with lvt topology, which then interpenetrates. In BUT-44, each Zr6-based cluster is coordinated with eight BTEB4− ligands to give a single 3D 4,8-connected scu network, which then doubly interpenetrates to give the first example of interpenetrated 4,8-connected Zr(iv)-MOF. Studies on their stability and gas adsorption properties demonstrate that BUT-44 shows higher stability in NaOH solution of pH 10 and 1 M HCl aqueous solution. More interestingly, both MOFs represent good gas adsorption selectivities for C2H2 over CO2 and CH4, suggesting potential application in gas separation. [ABSTRACT FROM AUTHOR]

By utilizing symmetrical pentacarboxylate ligands, 3,5-di(2′,5′-dicarboxylphenyl)benzoic acid (H5L1) and 3,5-di(2′,4′-dicarboxylphenyl)benzoic acid (H5L2), two novel porous Zn-MOFs, [Zn5(μ3-H2O)2(L1)2]·3DMA·4H2O (CTGU-3) and [Zn3(μ3-OH)L2(H2O)3]·H2O (CTGU-4) have been synthesized under solvothermal conditions. CTGU-3 and CTGU-4 exhibit 3D microporous frameworks with flu and dia topologies and possess unique secondary building units [Zn5(μ3-H2O)2(RCO2)6] and [Zn3(μ3-OH)(RCO2)3], respectively. Such porous systems create a unique space or surface to accommodate Ag nanoparticles (Ag NPs), which could efficiently prevent Ag NPs from aggregation and leaching. In this work, two new Ag@Zn-MOF composites, denoted as Ag@CTGU, have been successfully fabricated through solution infiltration, for the reduction of nitrophenol. Compared with CTGU-4, CTGU-3 shows enhanced catalytic efficiency toward the reaction when it is used as a catalyst support of Ag NPs. Moreover, gas sorption and luminescence properties of two compounds were also investigated. [ABSTRACT FROM AUTHOR]

A super-stable multifunctional terbium(iii)–organic framework, namely {[Tb(TATAB) (H2O)2]·NMP·H2O}n (Tb-MOF, H3TATAB = 4,4′,4′′-s-triazine-1,3,5-triyltri-m-aminobenzoic acid, NMP = N-methyl-2-pyrrolidone) was synthesized. Tb-MOF exhibits a 2D sql structure with binuclear [Tb2(COO)4(H2O)4]2+ units as 4-connected nodes, and free water and NMP molecules are inserted between 2D layers through hydrogen-bonding interactions, forming a sandwich-type architecture. Observably, such a framework remains intact in a remarkable variety of environments such as common solvents and aqueous solutions with metal cations and inorganic anions, as well as with a pH ranging from 1 to 13. In particular, Tb-MOF can not only detect small organic molecules, metal cations and inorganic anions with high sensitivity and high selectivity, but also can accurately detect explosive 2-nitrophenol, 3-nitrophenol, 4-nitrophenol and 2,4,6-trinitrophenol in water. Its luminescence quenching response to Fe3+ and Cr2O72− ions can be explained in terms of the competitive absorption mechanism. In addition, the luminescence intensity of Tb-MOF is strongly correlated with the pH value in a pH range from 1 to 13. Thus, this material can be potentially used as a multi-responsive luminescent sensor. [ABSTRACT FROM AUTHOR]

Three polyoxovanadate-based metal–organic polyhedra (denoted as VMOP-1, -2, and -3), adopting isostructural discrete octahedral cage geometries, were successfully synthesized under solvothermal conditions. These structures are all built up from the same pentavanadate {V5O9Cl} cluster connected by linear bidentate ligands (H2L1 = H2BDC, H2L2 = H2BDC-NH2, H2L3 = H2BDC-Br), respectively. [ABSTRACT FROM AUTHOR]

Seven new coordination polymers, namely, [Zn(L)(bdc)]·2H2O (1), [Zn(L)(2-NH2-bdc)]·2H2O (2), [Zn(L)(bdc)]·1.75DMF·0.5H2O (3), [Zn(L)(oba)]·H2O (4), [Co(L)(oba)]·H2O (5), [Cd2(L)2(bdc)(NO3)2]·2DMF (6) and [Cd(L)(ndc)(H2O)] (7) (L = 4-amino-3,5-bis(4-imidazol-1-ylphenyl)-1,2,4-triazole, H2bdc = 1,4-benzenedicarboxylic acid, 2-NH2-H2bdc = 2-amino-1,4-benzenedicarboxylic acid, H2oba = 4,4′-oxydibenzoic acid and H2ndc = 1,4-naphthalenedicarboxylic acid), have been synthesized. The structures were determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, IR, and thermogravimetric (TG) analysis. 1 and 2 feature a similar three-fold interpenetrating network combined with interdigitation which extends the structure into a three-dimensional framework. 3 is a two-fold interpenetrating framework showing intralayer porosity and interdigitation. Compounds 1 and 3 represent a pair of supramolecular isomers where structural motifs and different interpenetration modes exist; compounds 4 and 5 are isostructural and display the same three-fold interpenetrating framework where two types of interlaced triple-stranded helices A and B can be found. The triple-stranded helices with opposite chirality for each type are distributed in adjacent layers. Compound 6 exhibiting a unique simultaneous threading fashion of adjacent polymeric motifs gives the novel (2D → 3D) polythreaded array where coordinated NO3− anions act as the dangling ligands. Compound 7 is a 6-connected 3D self-penetrating network where right- and left-handed single-stranded helical chains (AR and AL) and interlaced triple-stranded helices (BR and BL) coexist. The luminescence properties of compounds 1–7 were also measured and discussed. [ABSTRACT FROM AUTHOR]

The formation of metal–organic frameworks (MOFs) under given reaction conditions depends on various factors including reaction duration, temperature, used solvent, system pH, and others. Among them, the reaction duration is relatively less investigated. In this work, based on a Cu(ii)-MOF system, the reaction duration was found to play an important role in directing the formation of two different products, (NH2(CH3)2)[Cu12(DDPN)6(H2O)10Cl] (BUT-301) on shorter reaction time and (NH2(CH3)2)2[Cu(DDPN)] (BUT-302) on longer reaction time, when CuCl2 reacted with 3,5-di(3,5-dicarboxylphenyl)nitrobenzene (H4DDPN) in a DMA/MeOH mixed solvent at 120 °C. With increasing the reaction duration, BUT-301 can transform into BUT-302. Both MOFs have three-dimensional (3D) framework structures. BUT-301 is constructed from paddle-wheel Cu2(COO)4 units and DDPN4– ligands as four-connected linkers, while BUT-302 is assembled from mononuclear Cu(ii) centers connecting the ligands as also four-connected linkers but in a monodentate coordination fashion. N2 adsorption confirmed that both MOFs are porous materials with the Brunauer–Emmett–Teller (BET) surface areas of 1953 and 561 m2 g−1, respectively. Interestingly, both BUT-301 and -302 show selective adsorption properties of C3H4 over C3H6. The C3H4/C3H6 adsorption selectivities were calculated to be 1.9 and 4.4 at 0.1 bar and 298 K by the ideal adsorbed solution theory (IAST) for a 1 : 99 C3H4/C3H6 mixture, respectively. [ABSTRACT FROM AUTHOR]