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A newly constructed hexanuclear cadmium metal–organic framework (MOF) exhibits a highly selective and sensitive fluorescence‐quenching response toward Fe 3+ ions, which is attributable to the coaction of absorption competition and an energy‐transfer mechanism.

Three new mixed-ligand divalent coordination polymers (CPs) {[Zn3(L)(1,4-bdc)3]·2DMF}n (1), {[Zn2(L)(2,6-ndc)2]·3DMF}n (2) and {[Cd2(L)3(2,6-ndc)2]}n (3) [L = 9,10-di(pyridine-4-yl)anthracene, 1,4-H2bdc = 1,4-benzenedicarboxylic acid, 2,6-H2ndc = 2,6-naphthalenedicarboxylic acid] have been prepared and well characterized by elemental analyses, infrared spectroscopy, single-crystal X-ray diffraction techniques, powder X-ray diffraction patterns and thermogravimetric analyses. The crystal structure analyses of coordination polymers (CPs) reveal that all the complexes 1–3 have the three-dimensional (3D) coordination networks. The structure of 1 can be simplified as a sqc3 3D 8-connected framework with the point symbol of (424·64). Particularly, in the presence of the linear 2,6-H2ndc auxiliary ligand, a double-deck interpenetrating pcu 3D network of 2 is assembled by 6-connecting framework with the point symbol of (412·63). Complex 3 exhibits a ttd 3D 5-connected net with a point symbol of (46·64). Further, the solid-state luminescent properties of the complexes 1–3 were measured and studied at room temperature.

In order to elucidate the effect of the structure on stability and gas adsorption performance, three porous Zn(II) metal–organic frameworks, NKU-106, NKU-107, and NKU-108, have been constructed. NKU-106 and NKU-107 assembled from acylamide functionalized tetracarboxylate ligand exhibit low stability and thereby poor gas adsorption ability. However, when one isophthalate moiety of the tetracarboxylate ligand is replaced with a pyrazole group, and the resulting NKU-108 shows improved thermal and chemical stability as well as good adsorption capacities with respect to CO2 and C2 hydrocarbons. This result demonstrates that coordination group optimization is an effective strategy to improve the stability and gas adsorption properties of metal–organic frameworks (MOFs) and thus provides very valuable information for future design and synthesis of porous MOFs for practical application.

In this paper, two 3D anionic metal–organic frameworks, [(CH3CH2)2NH2]·[Zn(BTC)1/3(PyC)]·1/2CH3CN·2H2O (NKU-102) and [(CH3CH2)2NH2]·[Zn2(BTC) (PyC)]·1.5H2O·DEF (NKU-103), were constructed from the same reaction system at different temperature. Though both are of anionic framework, NKU-102 possesses a sealed 3D framework based on octahedral cage and shows negligible adsorption capacity of organic dyes, whereas NKU-103 features an open triangular microchannel surrounded by two types of helical chains, and thus exhibits outstanding size-selective adsorption toward small cationic organic dyes.

The new functional ligand 5-(1H-pyrazole-4-carboxamido)isophthalic acid (H3L) reacts with CoSO4·7H2O to form a new three-dimensional metal–organic framework, [Co4(HL2−)4(DMF)2(H2O)2]n·solvent (1) with a new (3,6)-connected topology. 1 exhibits one-dimensional polar channels with approximate dimensions of 6.0 × 8.0 A2 decorated with accessible functional sites. These sites contribute to enhanced CO2 uptake (103.2 cm3 g−1 at 273 K and 1 bar) and CO2/CH4 selectivity (7.25 for CO2/CH4 = 50 : 50; 8.59 for CO2/CH4 = 5 : 95) at 298 K and 1 bar. DFT calculations were also performed to elucidate the binding sites. These results suggest that complex 1 is an attractive candidate for CO2 adsorption and separation.

Water instability is a crucial limiting factor in the practical application of most fluorescent metal-organic frameworks (MOFs). Here, by introducing a fascinating double-helical structure generated through dense stacking of organic ligands, a water-stable fluorescence MOF has been synthesized, namely, [Cd2(tib)2(bda)2]·(solvent)n (1) [tib =1,3,5-tris(1-imidazolyl) benzene; H2bda = 2,2'-biphenyl dicarboxylic acid]. This helical structure helps to enhance the stability of 1 against common organic solvents and water, even acid/base aqueous solutions with a pH value ranging from 3 to 11. Furthermore, this material can be a potential fluorescent sensor for ketones.

A series of porous pillar-layer frameworks have been prepared with 1,3,5-tris(p-imidazolylphenyl)benzene (tipb) as the main ligand and dicarboxylic acids as coligands. Our studies have demonstrated that tipb is prone to form a 63 layer with targeted metal ions, which could be utilized to construct pillar-layer frameworks. The structure and porous properties of the resulting metal–organic frameworks could be tuned by modifying the size, geometry, and functional groups of the coligands (pillars). Moreover, gas adsorption measurements revealed that both complexes 1 and 2 exhibit selective adsorption of H2 over N2 for the pore-size effect.

The conversion from a [2 + 2] nested double-helical column, {[Mn2(ptptp)(suc)(H2O)2]·1.5H2O}n (1), to a cationic spiral staircase, {[Mn2(ptptp)(suc)0.5(H2O)3]·Br·0.5H2O}n (2), has been achieved through ionic liquid anion stimulations under solvothermal conditions. The conversion does not change the antiferromagnetic interactions.