•Nanoscale IR-MOFs are synthesized by the improved coordination modulation method.•Zinc acetate provides a zinc source, adjusts the pH, and acts as capping agent.•IR-MOF films on ITO glass are formed by dipping-coating-secondary-growth.•IR-MOF films have low k values, good mechanical strength and hydrophobicity.To explore the preparation of ultra-low k MOFs material, uniform nanosized isoreticular metal−organic frameworks (IR-MOFs) nanocrystals were prepared by the optimized coordination modulation method and the IR-MOF nanocrystals were used to form IR-MOF films on an ITO glass by dip coating and secondary growth. The continuous thin MOF-3, MOF-5 and MOF-10 films supported on ITO glass had a dielectric constant of 1.2, 2.1 and 4.8 at 2 MHz respectively, and good mechanical strength, adhesion, and hydrophobicity. However, probably due to the presence of the strong polarity of NH2-BDC in MOF-3, and the presence of N–H moieties on grain boundaries, crystal surfaces, and internal crystal defects, which abundantly adsorb water, the MOF-3 film has higher low-k at 100 kHz. For the MOF-10 film with high low-k at 100 kHz, due to the low BET surface area, it could be related to the strong polarity of solvent molecular trapped in the films.

•Co-MOF ZIF-67 nanocrystals were synthesized by coordination modulation method.•Co3O4 hollow spheres were prepared by pyrolysis of ZIF-67.•The obtained Co3O4 own the high density of active metal sites.•Co3O4 modified electrode could effectively detect H2O2.•The sensor showed high sensitivity, low detection limit, and broad linear range.Hollow-sphere Co3O4 nanoparticles were successfully synthesized by direct pyrolysis of cobalt-containing zeolitic imidazolate frameworks (ZIF-67) precursor. The transformation process from ZIF-67 to Co3O4 hollow sphere was characterized by powder X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and thermal gravimetric analysis. It is found that the as-prepared Co3O4 nanoparticles possesses uniform hollow spherical structure with many voids on the surface. It's worth noting that the high density of metal sites, the ordered arrangement of Co, as well as the uniform crystal size and regular morphology was inherited from ZIF-67, resulting in an excellent accessibility of Co. The resulting Co3O4 hollow sphere was exploited as an electrocatalyst for sensitive H2O2 detection in an alkaline medium. The Co3O4 hollow sphere modified glassy carbon electrode exhibited a fast response time (within 3s), a high sensitivity of 120.55 μA/mM (959.79 μA∙mM−1∙cm−1), a broad linear range from 0.4 μM to 2.2 mM, a detection limit of 0.105 μM (S/N=3), and good stability and selectivity, suggesting its excellent performance towards H2O2 detection.High-activity nanoscale Co3O4 hollow sphere has been developed using cobalt-containing imidazolate MOF framework ZIF-67 as precursor. The obtained cobalt oxide exhibited excellent electrocatalytic ability toward H2O2, with a high sensitivity, a low detection limit, a broad linear sensing range, and a short response time.

A green coordination modulation method has been successfully exploited to fabricate lanthanide coordination polymer Tb(BTC)(H2O) via environmentally friendly ethanol and alkaline additive. Fascinating hierarchical architectures, including rod-like crystals, dual-core shelled peanut-like crystals and double-head dandelion-like crystals were obtained through exploring the reaction parameters. The structures of the samples were confirmed by powder X-ray diffraction, and the morphologies were characterized by SEM. Furthermore, details of the formation mechanism of the resulting crystal morphologies were deduced. The studies of the photoluminescence properties reveal that the hierarchical architectures of these coordination polymers exhibit green emission, corresponding to the 5D4/7FJ (J = 6, 5, 4, 3) transitions of the Tb3+ ions under UV light excitation. Outstandingly, double-head dandelion-like crystals with the strongest photoluminescence intensity display highly sensitive and selective sensing for heavy metal ions, and the probable sensing mechanism was discussed.

Three types of modulators, including sodium formate, sodium acetate and triethylamine were used to tailor the morphology and size of HKUST-1 crystals by “coordination modulation method”. Through exploring the reaction parameters during the synthesis of HKUST-1, fascinating crystals morphologies, including hierarchical octahedral-shape crystals and nanocrystals were obtained by a solvothermal treatment. This paper discloses two essential functions of the modulator for the fabrication of uniform nanocrystals: Adjusting the proper acid–base environment of the reaction medium which governs the nucleation process and capping groups capable of inhibiting crystallites from growing. Moreover, samples were fully characterized by various techniques and the formation mechanism of the hierarchical octahedral-shape crystals was deduced.Graphical abstractFascinating crystals morphologies, including hierarchical octahedral-shape crystals and nanocrystals were obtained by employing various modulators, including sodium formate, sodium acetate and triethylamine. This graphical discloses two essential parameters for miniaturizing the size of HKUST-1 crystals to the nanometer scale. One is the proper acid–base environment of the reaction medium which governs deprotonation of the organic linker and, hence, the nucleation process. The other is the use of capping groups capable of inhibiting crystallites from growing. These findings have important significance for extending this method to the synthesis of other types of NMOF crystals and may help to perform size- and shape-controlled syntheses of nano- and microscale HKUST-1 bulk materials and supported HKUST-1 membranes/films in a more rational way.Highlights► Two functions of modulator to prepare nanosized MOFs crystal have been disclosed. ► Modulator adjusts the pH, and owns the capping groups. ► Sodium formate as a modulator, spherical monodisperse nanocystals can be prepared. ► Microcrystal has been obtained with addition of sodium acetate as modulator. ► Hierarchical octahedral-shape crystal was synthesized using the TEA as modulator.

The mono- and bi-metallic flower-like infinite coordination polymer were synthesized by simple coordination-modulation method using sodium acetate as capping agent. The structure was characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Based on a series of comparative experimental results, we have deduced that the possible formation mechanism of these Dy-flower-like microspheres via a three-step process.The mono- and bi-metallic flower-like infinite coordination polymer were synthesized by simple coordination modulation method using sodium acetate as capping agent. The possible formation mechanism of these Dy-flower-like superstructure have been deduced via a three-step process: 1. Generation of enormous amount of nanoparticles. 2. Nanoparticles continuously aggregate into 2D nanoflakes owing to the Ostwald ripening, 3. The flower-like superstructures appear due to the fractal splitting growth.Highlights► Coordination modulation induced synthesis of flower-like ICPs. ► Uniform microspheres built from packed layers of two dimensional microflakes. ► Microflakes split out from the center part and take on a flower-like appearance. ► The formation mechanism of flower-like superstructure has been deduced.