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Herein, two new water-stable magnetic frameworks, [Cu1.5(L)(H2O)]·2H2O (1) and [Co4(L)2(CH3CN)(OH)2(H2O)4]·3H2O (2) (H3L = 5-((4-carboxypyridin-2-yl)oxy) isophthalic acid), were synthesized by a solvothermal method in similar reaction systems and characterized by infrared spectroscopy, powder X-ray diffraction and thermogravimetric measurements. Due to their different metal ions, 1 shows a trinodal (4,4,4)-connected three-dimensional (3D) framework that possesses 1D channels based on [Cu2(COO)4] paddle-wheel secondary building units (SBUs), whereas 2 is a 2D layered network based on tetranuclear [Co4(COO)6(μ3-OH)2] SBUs and reveals a (3,6)-connected kgd topological structure. The gas adsorption explorations demonstrated that 1 exhibited commendable selectivity for CO2 over CH4. Moreover, both 1 and 2 showed different degrees of antiferromagnetic exchange action.

Five coordination polymers, {[Co3(L)2(H2O)2]·4H2O} (1), {[Cd3(L)2(NMP)2]} (2), {[Cu(HL)]·NMP} (3), {[Cd(HL)(2,2′-bipy)]} (4) and {[Co(HL)(4,4′-bipy)(H2O)2]} (5) with different dimensional structures, have been solvothermally synthesized from a trifunctional N,O-building block, 5-(3,4-dicarboxylphenoxy)nicotinic acid (H3L) that combines three distinct types of functional groups (COOH, N-pyridyl, and O-ether), and an auxiliary co-ligand, 2,2′-bipy or 4,4′-bipy (2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine). H3L contains three different types of functionalities and has eight potential coordination sites, which results in diverse coordination patterns and different dimensionalities depending on the reaction conditions. Complexes 1–3 display 2D layer structures with 1D channels, 4 shows a 2D + 2D → 2D interpenetrated wavy structure, while 5 exhibits a 1D chain structure. 1 demonstrates an effective storage capacity for CO2 as well as high selectivity for CO2 over CH4 under ambient conditions. The magnetic properties revealed antiferromagnetic behaviors for complexes 1, 3 and 5. Also, the alternating-current susceptibility of 5 displays slow magnetic relaxation, showing interesting magnetic behavior with an effective energy barrier of 8.98 K.

Five coordination polymers, {[Zn(dtp)]·H2O} (1), {[Zn(dtp)]·2CH3OH·NMP} (2), {[Mn2(dtp)2(H2O)4]·12(H2O)} (3), {[Mn(Hdtp)(Cl)]} (4) and {[Mn(dtp)(H2O)]·1.5H2O} (5) with different dimensional structures, have been solvothermally synthesized by utilizing the H2dtp ligand (H2dtp = 4′-(3,-5-dicarboxyphenyl)-2,2′:6′,2′′-terpyridine). All complexes are characterized by single-crystal X-ray diffraction, elemental analysis, IR spectra, thermogravimetric analysis (TGA) and powder X-ray diffraction (PXRD). The Zn(II)-based complexes 1 and 2 display a 2D wavy layer structure and a 3D porous framework with a 1D channel, respectively. The three Mn(II)-based complexes 3–5 exhibit two 1D chain and one 2D layer structures, respectively. Complexes 1 and 2 reveal their luminescence properties, whereas complexes 3–5 display an antiferromagnetic exchange. Meanwhile, an unusual stepwise adsorption for CO2 was also observed in 2.

Structural transformation has aroused wide interest and has emerged as a promising approach for the design and synthesis of novel coordination polymers. In this work, we found interesting structural transformation phenomena triggered from a nickel coordination polymer (CP). Two temperature-dependent two-dimensional (2D) CPs, 1 and 2 were synthesized from hydrothermal reactions, while the other two CPs, 2D 3 and 3D 4 were the products of the in situ thermal decomposition of 1. Interestingly, 1 could undergo methanol-mediated transformation to afford 2 and 2 might convert to 1 under the condition of adding bipy in water. The multi-step conversions from 1 to 3 and 3 to 4 triggered by heat treatment in the solid state accompany the very rare dynamic response of a sequential release of coordinated water and partial organic ligands. More importantly, the mechanism of the transformation has also been studied in detail. Moreover, 3 could revert back to 1 quickly upon exposure to air, and this reversible process of dehydration–rehydration could be repeated at least ten times, which could highlight the application for their use in moisture sensors.

Solvothermal reactions of Cu(NO3)2 and 4,4′-([3,4′-bipyridine]-2′,6′-diyl)dibenzoic acid (H2L1), 3,3′-([4,4′-bipyridine]-2,6-diyl)dibenzoic acid (H2L2), or 4,4′-([4,4′-bipyridine]-2,6-diyl)dibenzoic acid (H2L3) yielded three new metal-carboxylate frameworks (MCF-28, MCF-29 and MCF-30) with a common formula [Cu2(L)2] (H2L = pyridyldicarboxylic acid). X-ray crystallography showed that MCF-28, MCF-29, and MCF-30 are three-dimensional (3,6)-connected rtl, eea and pyr networks, respectively, based on 3-connected tripodal ligands and 6-connected Cu2(RCOO)4(py)2 units (RCOO and py denote carboxylate and pyridyl groups, respectively). Thermogravimetry, powder X-ray diffraction, and gas adsorption measurements indicated that the three compounds became shrunk and amorphous structures after guest removal. Interestingly, single-crystal X-ray diffraction showed that MCF-28 exhibited drastic temperature-induced framework breathing.

Two isostructural 3D microporous metal–organic frameworks, which show a 6-connected (48·66·8) self-penetrating net, contain two different narrow-sized channels functionalized by amino groups on the pore surface. In particular, both of them show exceptional stability and a high selectivity for CO2 over N2 at 298 K.

Metal–organic frameworks (MOFs) have become a rapidly expanding research topic in the fields of synthetic chemistry and materials science in recent years. Entanglement is often considered to be an important phenomenon in MOFs. Currently, a large number of entangled metal–organic frameworks (EMOFs) have been yielded and documented well in the literature. The structure–property relationships of an EMOF can be directed and fine-tuned not only by the starting materials, i.e. metal ions/clusters and organic ligands, but also by the various reaction conditions, including reaction temperature, pH value, and molar ratio of reactants etc. In this highlight, we carefully attempt to analyze and summarize the key factors which significantly influence the formation of EMOFs, and we hope this work may provide some primary guide information to the predesign and construction of desired EMOFs.

An unprecedented 3D entangled framework, {[Co(bib)(hoip)]·6H2O}n (1), has been synthesized by using rigid and flexible mixed-ligands, which represents to the best of our knowledge, the first example of one-fold inclined 1D → 3D polycatenated networks built by the vertical interlocking of novel interweaving triple-stranded helices sharing the same CoII nodes.

Two new zinc(II) microporous metal–organic frameworks (MOFs), [Zn(dcpy)(bpe)0.5]·3H2O (1) and [Zn(dcpy)(bpe)0.5]·(CH3OH)0.5·(H2O)0.5 (2) constructed from the same initial materials 3-(2',5'-dicarboxylphenyl)pyridine (H2dcpy), 1,2-di(4-pyridyl)ethylene (bpe) and Zn(NO3)2·6H2O, exhibiting varying architectures from a 2-fold parallel interpenetrated structure to a 4-fold parallel interpenetrated framework were synthesized by changing the reaction solvents. Complexes 1 and 2 are supramolecular isomeric and both show 2-nodal (3,4)-connected networks, which represent rare dmc and coe topology styles, respectively. Interestingly, 1 presents reversible crystal structural transformation upon dehydration and rehydration, whereas 2 transforms into a new crystal phase 2a after desolvated. When dipping 2a into a DMF/CH3OH/H2O mixed solvent, another new crystal phase 2b can be formed, moreover, 2a and 2b could convert to each other through desolvation and solvation. In particular, the dehydrated 1a shows a high selective gas sorption for H2 over N2 at 77 K and high selectivity for CO2 over N2 at 293 K. The photoluminescence behaviors of 1 and 2 are also discussed.

Two new complexes {[Co(dcpy)(bipy)0.5]·H2O} (1) and {[Co(dcpy)(bipy)0.5(H2O)]·2H2O} (2) constructed from the same initial materials Co(NO3)2·6H2O, 3-(2′,5′-dicarboxylphenyl)pyridine (H2dcpy) and 4,4′-bipyridine (bipy), exhibiting varying architectures from a 3D 4-fold interpenetrated framework to a 2D layer-type porous coordination polymer (PCP) were synthesized by changing the reaction solvent. In particular, the dehydrated 2 shows a high selective gas sorption for H2 over N2 at 77 K and high selectivity for CO2 over N2 and CH4 at 293 K.

A series of new metal–organic coordination complexes, [Zn(cpds)(H2O)2]n (1), {[Zn(cpds)(4,4′-bipy)]·6H2O}n (2), {[Zn(cpds)(bpe)]2·0.5(bpe)·4H2O}n (3), [Cu(cpds)(2,2′-bipy)(CH3OH)]2·2H2O (4), {[Cu(cpds)(4,4′-bipy)(H2O)2]·2.24H2O}n (5), {[Cu(6-sinic)(4,4′-bipy)0.5]·CH3OH·H2O}n (6), [Cd2(6-mna)2(phen)]n (7), and {[Cd(cpds)(bpe)]·2.2H2O}n (8) were prepared by self-assembly of disulfide derivative of the nicotinate, 6,6′-dithiodinicotinic acid (H2cpds) with transition metal ions in the absence of different N-donor ligands (4,4′-bipy = 4,4′-bipyridine, 2,2′-bipy= 2,2′-bipyridine, phen = 1,10-phenanthroline, bpe = 1,2-bis(4-pyridyl)ethene, 6-sinic = 6-sulfinto-nicotinate, 6-mna = 6-mercaptonicotinic acid). X-Ray structure analyses of 1–8 reveal their structure ranging from the discrete unit (0D) (4), one-dimensional (1D) (1, 5), two-dimensional (2D) (7), non-interpenetrating 3D porous coordination polymers (6, 8), 2-fold interpenetrated structure (2) to a 5-fold interpenetrating framework (3), which mainly due to the differences in the bridging modes of cpds2− and the effect of the secondary ligands. Interestingly, in the complexes 6 and 7, the starting H2cpds reagent is converted into new ligands (6-sinic in 6 and 6-mna in 7) under solvothermal condition viain situ cleavage of S–S bond. In addition, thermogravimetric analyses, X-ray powder diffractions and the fluorescent properties of complexes 1, 2, 3, 7, 8 have been investigated.

The solvothermal reactions of CuCN with two structure-related flexible 4-pyridyl dithioether ligands, bis(4-pyridylthio)methane (L1) and 1,2-bis(4-pyridylthio)ethane (L2), generated two novel three-dimensional (3D) coordination polymers: [(CuCN)5(L1)2]n (1) and [(CuCN)3(L2)]n (2), respectively. Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric analyses. Complex 1 is constructed by the interconnection of CuCN layers with L1 pillars to form an interesting self-penetrating 123 topological network with characteristic of four distinct helical chains. In 2, each L2 acting as a quadridentate μ3-bridge connects Cu atoms from three uncommon meso-helical CuCN chains, to give 3D framework containing 1D tubes constructed by two types of helical chains with opposite chirality. 2 exhibits a 3-fold interpenetrating network with a rare (62·10)2(6·102) topology. In addition, the solid state samples of 1 and 2 exhibited different luminescent properties at room temperature.