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A new glass forming method is essential for broadening the scope of liquid and glassy metal–organic frameworks due to the limitations of the conventional melt-quenching method. Herein, we show that in situ mechanical vibration can facilitate the framework melting at a lower temperature and produce glassy metal–organic frameworks (MOFs) with unique properties. Using zeolitic imidazolate framework (ZIF)-62 as a concept-proofing material, in situ mechanical vibration enables low-temperature melting at 653 K, far below its melting point (713 K). The resultant vibrated ZIF-62 glass exhibited a lower glass transition temperature of 545 K, improved gas accessible porosity, and pronounced short-to-medium range structures compared to the corresponding melt-quenched glass. We propose that vibration-facilitated surface reconstruction facilitates pre-melting, which could be the cause of the lowered melting temperature. The vibration assisted method represents a new general method to produce MOF glasses without thermal decomposition. [ABSTRACT FROM AUTHOR]

Glassy and liquid state metal–organic frameworks (MOFs) are emerging type of materials subjected to intense research for their rich physical and chemical properties. In this report, we obtained the first glassy MOF that involves metal‐carboxylate cluster building units via multi‐stage structural transformations. This MOF is composed of linear [Mn3(COO)6] node and flexible pyridyl‐ethenylbenzoic linker. The crystalline MOF was first perturbed by vapor hydration and thermal dehydration to give an amorphous state, which can go through a glass transition at 505 K into a super‐cooled liquid. The super‐cooled liquid state is stable through a wide temperature range of 40 K and has the largest fragility index of 105, giving a broad processing window. Remarkably, the super‐cooled liquid can not only be quenched into glass, but also recrystallize into the initial MOF when heated to a higher temperature above 558 K. The mechanism of the multi‐stage structural transformations was studied by systematic characterizations of in situ X‐ray diffraction, calorimetry, rheological, spectroscopic and pair‐distribution function analysis. These multi‐stage transformations not only represent a rare example of high temperature coordinative recognition and self‐assembly, but also provide new MOF processing strategy through crystal‐amorphous‐liquid‐crystal transformations. [ABSTRACT FROM AUTHOR]

A series of highly connected metal-organic frameworks (MOFs), [Co8(O)(OH)4(H2O)4(ina)8](NO3)2 ⋅2 C2H5OH ⋅4 H2O ( 1), [Co8(O)(OH)4(H2O)4(pba)8](NO3)2 ⋅8 C2H5OH ⋅28 H2O ( 2), and [Co8(O)(OH)4(H2O)4(pbba)8](NO3)2 ⋅guest ( 3), in which ina=isonicotinate, pba=4-pyridylbenzoate, and pbba=4-(pyridine-4-yl)phenylbenzoate, is reported. These MOFs contain a new secondary building unit (SBU), with a square Co4(μ4-O) central unit having the rare μ4-O2− motif, which is decorated by the other four peripheral cobalt atoms through μ3-OH in a windmill-like shape. This SBU holds 16 divergent connecting organic ligands, pyridyl-carboxylates, to form three different frameworks. The high porosity of desolvated 2 is shown by the efficient gas absorption of N2, CO2, CH4, and H2. In addition, 1 and 2 exhibit unusual canted antiferromagnetic behavior with spin-glass-like relaxation, with blocking temperatures that are fairly high, 20 K ( 1) and 10 K ( 2), for cobalt materials. The relationship between the metal clusters and linkers has been studied, in which the size and rotational degrees of freedom of the ligands are found to control the topology, gas sorption, and magnetic properties. [ABSTRACT FROM AUTHOR]

The interest in metal-organic frameworks (MOFs) is rapidly expanding because of their fascinating architectures and intriguing topologies which allowed for potential applications in gas storage, separation, heterogeneous catalysis, and several other areas. As suitable chromatographic separation media, several MOFs have been employed as stationary phase for gas chromatography and high-performance liquid chromatography. In this work we report the use of a mixed ligands rod-spacer MOF [Mn 3 (HCOO) 2 ( D -cam) 2 (DMF) 2 ] n as coating material for capillary column of gas chromatographic separation of a series of biochemical important compounds having linear alkyl hydrocarbon (aldehyde, alcohol and ester), aromatic hydrocarbon with two phenyls (ether, ester and ester with alcohol) and aromatic hydrocarbon (ester, ester with amino and two esters). The mixture of functional ligands, good thermal and chemical stabilities and host-guest interaction sites of the MOF are attributes to the good efficiency in gas chromatographic separation. [ABSTRACT FROM AUTHOR]

[Display omitted] A pillared-layer MOF constructed from two matched and quite long linkers of thiadiazole functionalized dicarboxylate and dipyridine, exhibits selective adsorption of CO 2 over CH 4 and N 2. This work provides new insight into the pore surface modification and broadens the horizons to rational design mixed-ligands MOF with demanding pore environment for specific application. • Well-matched long mixed linkers facilitate highly porous and rigid pillared-layer MOF. • The Co(II)-MOF is structural stable in water, pH = 1 HCl and pH = 12 NaOH aqueous solution. • The 1D narrowed channels with rich thiadiazole groups contribute to selective CO 2 adsorption. The high-efficiency CO 2 separation using metal–organic frameworks (MOFs) is crucial in CO 2 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 [Co 2 (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 (H 2 btd) 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 CO 2 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 CO 2 over N 2 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. [ABSTRACT FROM AUTHOR]

A pillar-layered MOF is constructed from 1,2,4-triazole extended (4,4)-grid layer, which is pillared by inclined dicarboxylate. Benefited from the good structure stability in various organic solvents, water, and either acidic or alkaline condition, the highly fluorescent 1 is used to selectively sensing Fe3+ with a low detection limit in methanol and aqueous solution, through quenching effect stemming from weak binding between uncoordinated N atoms in the thiadiazole and Fe3+. [Display omitted] • A pillared-layer MOFs is constructed from (4,4)-grid layer pillared by inclined dicarboxylate. • The MOFs is structural stable in water, pH = 3 HCl and pH = 12 NaOH aqueous solution. • Selective sensing of Fe3+ with low detection limit is realized by fluorescence quenching. The pillared-layer Metal–Organic Framework (MOF) enjoys good tunability and rich functionality, yet highly relies on rational combination of mixed ligands. A new MOF formulated as [Zn 2 (trz) 2 (btdb)]·4DMF (1 , trz = 1,2,4-triazole, H 2 btdb = 4,4′-(benzo[c][1,2,5]thiadiazole-4,7-diyl) dibenzoic acid) is constructed from a [Zn 2 ] node based (4,4)-grid layer that pillared by inclined a highly fluorescent dicarboxylate linkers. The rigid [Zn 2 (trz) 2 ] layer coupled with hydrogen bonding encompassed Zn-carboxyl linkage endow the MOF desired high stability. The crystalline structure of 1 maintains well in harsh conditions including pH = 3 HCl and pH = 12 NaOH aqueous solution for more than 24 h. With high void fraction of 42.7%, the interconnected 3D channels sized at 4.0–8.8 Å guarantee sufficient exposure of thiadiazole in the pillar ligand as potential sensing site. With bright fluorescence of 1 , Fe3+ ions can be selectively and specifically detected in both aqueous and non-aqueous solution through quenching mechanism, given a detection limit of 3.1 and 17.0 μM in methanol and H 2 O solution, respectively. [ABSTRACT FROM AUTHOR]