Metal−organic frameworks (MOFs) have been widely recognized as one of the most fascinating classes of materials from science and engineering perspectives, benefiting from their high porosity and well-defined and tailored structures and components at the atomic level. Although their intrinsic micropores endow size-selective capability and high surface area, etc., the narrow pores limit their applications toward diffusion-control and largesize species involved processes. In recent years, the construction of hierarchically porous MOFs (HP-MOFs), MOF-based hierarchically porous composites, and MOF-based hierarchically porous derivatives has captured widespread interest to extend the applications of conventional MOF-based materials. In this Review, the recent advances in the design, synthesis, and functional applications of MOF-based hierarchically porous materials are summarized. Their structural characters toward various applications, including catalysis, gas storage and separation, air filtration, sewage treatment, sensing and energy storage, have been demonstrated with typical reports. The comparison of HP-MOFs with traditional porous materials (e.g., zeolite, porous silica, carbons, metal oxides, and polymers), subsisting challenges, as well as future directions in this research field, are also indicated.

We explored the use of PVP-Au NPs as nucleation seeds for zeolitic imidazolate framework-8 (ZIF-8) to selectively synthesize Au@ZIF-8 single- or multi-core-shell structures by epitaxial growth or coalescence of nuclei. Photocatalytic oxidation of benzyl alcohol was studied based on LSPR-induced light absorption.

The single ion magnetic properties of Co(ii) are affected by the details of the coordination geometry of the ion. Here we show that a geometry close to trigonal prismatic which arises when the ligand 6,6'-((1Z)-((piperazine-1,4-diylbis(propane-3,1-diyl))bis(azanylylidene))bis(methanylylidene))bis(2-methoxyphenol) coordinates to Co(ii) does indeed lead to enhanced single-ion behaviour as has previously been predicted. Synthesis of the compound, structural information, and static as well as dynamic magnetic data are presented along with an analysis using quantum chemical ab initio calculations. Though the complex shows a slight deviation from an ideal trigonal prismatic coordination, the zero-field splitting as well as the g-tensor are strongly axial with D = -41 cm and E < 0.01 cm. For the lowest Kramers doublet (S = 1/2) g = 7.86 and g < 0.05 were found. In contrast, the second Kramers doublet possesses a rhombic g-tensor with g = 2.75 and g = 4.35. Due to large spin-orbit coupling resulting in very different g tensors, it is not possible to simulate the temperature dependence of the magnetic susceptibility with a spin Hamiltonian of the form H = D(S - S(S + 1)/3) + E(S - S) + μgS·B using an effective spin S = 3/2. Calculations on model complexes show the influence of the coordinating atoms and the deviation from the ideal trigonal prismatic coordination. As the distortion is reduced towards idealised D, the zero field splitting increases and the g-tensor of the second Kramers doublet also becomes axial.

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Four new isostructural lanthanide metal−organic frameworks (MOFs), namely {[Ln(DMTP-DC) 1.5 (H 2 O) 3 ]•DMF} n [H 2 DMTP-DC = 2′,5′dimethoxytriphenyl-4,4″-dicarboxylic acid; Ln III = Eu III (1), Gd III (2), Tb III (3), and Dy III (4)], have been synthesized and characterized. Single-crystal structure analysis reveals that 1−4 are three-dimensional Ln-MOFs with rich H-bonding of coordinated H 2 O molecules in the network channels. The X-ray diffraction patterns indicate that Ln-MOF 1 displays good stabilities in organic solvents and aqueous solutions with distinct pH values. Both 1 and 3 show characteristic emission of Ln III ions. Ln-MOF 1 can be used as a ratiometric fluorescence sensor for arginine and lysine in aqueous solution, and the detection limits are 24.38 μM for arginine and 9.31 μM for lysine. All 1−4 show proton conductivity related to relative humidity (RH) and temperature, and the maximum conductivity values of 1−4 at 55 °C and 100% RH are 9.94 × 10 −5 , 1.62 × 10 −4 , 1.71 × 10 −4 , and 2.67 × 10 −4 S•cm −1 , respectively. The value of σ increases with the decrease in ionic radius, indicating that the radius of the Ln III ions can regulate the proton conductivity of these MOFs. Additionally, 2 exhibits a significant magnetocaloric effect (MCE) with a magnetic entropy change (−ΔS m ) of 18.86 J kg −1 K −1 for ΔH = 7 T at 2 K, and 4 shows weak field-induced slow relaxation of magnetization. The coexistence of good fluorescence sensing capability, attractive proton conductivity, and relatively large MCE in Ln-MOFs is rare, and thus, 1−4 are potentially multifunctional MOF materials.

Tuning of relaxation of magnetisation through 3d metal ion variations in 3d2Dy2 butterflies.

The synthesis and characterization of three Dy2 compounds, [Dy2(HL1)2(NO3)4] (1), [Dy2(L2)2(NO3)4] (2), and [Dy2(HL3)2(NO3)4] (3), formed using related tripodal ligands with a central tertiary amine bearing picolyl and alkoxy arms, 2-[(2-hydroxy-ethyl)-pyridin-2-ylmethylamino]-ethanol (H2L1), 2-(bis-pyridin-2-ylmethylamino)-ethanol (HL2), and 2-(bis-pyridin-2-ylmethylamino)-propane-1,3-diol (H2L3), are reported. The compounds are rare examples of alkoxide-bridged {Dy2} complexes and display capped square antiprism coordination geometry around each Dy(III) ion. Changes in the ligand field environment around the Dy(III) ions brought about through variations in the ligand donors can be gauged from the magnetic properties, with compounds 1 and 2 showing antiparallel coupling between the Dy(III) ions and 3 showing parallel coupling. Furthermore, slow relaxation of the magnetization typical of SMM behavior could be observed for compounds 2 and 3, suggesting that small variations in the ligand field can have a significant influence on the slow relaxation processes responsible for SMM behavior of Dy(III)-based systems.