Yong-Zheng Zhang

A stable porphyrinic metal–organic framework pore-functionalized by high-density carboxylic groups for proton conduction

A new porphyrinic metal–organic framework (MOF), [Co(DCDPP)]·5H2O, was designed and constructed by using a bifunctional ligand, 5,15-di(4-carboxylphenyl)-10,20-di(4-pyridyl)porphyrin (H2DCDPP). This MOF features a three-dimensional framework structure with open channels, surrounded by high-density non-coordinating carboxylic groups, and exhibits a high proton conductivity of 3.9 × 10−2 S cm−1 at 80 °C and 97% relative humidity, higher than most conductive MOFs. Moreover, it also shows excellent stability in boiling water and cyclic proton conduction.

Functionalized Base-Stable Metal–Organic Frameworks for Selective CO2 Adsorption and Proton Conduction

Metal-organic frameworks (MOFs) have shown great potential for application in various fields, including CO2 capture and proton conduction. For promoting their practical applications, both optimization of a given property and enhancement of chemical stability are crucial. In this work, three base-stable isostructural MOFs, [Ni8 (OH)4 (H2 O)2 (BDP-X)6 ] (Ni-BDP-X; H2 BDP=1,4-bis(4-pyrazolyl)benzene, X=CHO, CN, COOH) with different functional groups, are designed, synthesized, and used in CO2 capture and proton conduction experiments. They possess face-centered cubic topological structures with functional nanoscale cavities. Importantly, these MOFs are fairly stable to maintain their structures in boiling water and 4 M sodium hydroxide solution at room temperature. Functionalization endows them with tunable properties. In gas adsorption studies, these MOFs exhibit selective adsorption of CO2 over CH4 and N2 , and in particular the introduction of COOH groups provides the highest selectivity. In addition, the COOH-functionalized Ni-BDP exhibits a high proton conductivity of 2.22×10-3  S cm-1 at 80 °C and approximately 97 % relative humidity.

Two interpenetrated metal–organic frameworks with a slim ethynyl-based ligand: designed for selective gas adsorption and structural tuning

In the design and construction of metal–organic frameworks (MOFs), the utilization of slim ligands is usually more inclined to form interpenetrated structures compared with bulky ones. The structural interpenetration can improve the framework stability and in some cases, enhance gas adsorption capacity and selectivity due to confined pores. In order to explore the structural control of MOFs and construct new MOFs with good selective gas adsorption ability, herein, a slim ethynyl-based 4-connected carboxylate acid ligand, 4,4′,4′′,4′′′-(benzene-1,2,4,5-tetrayltetrakis(ethyne-2,1-diyl))tetrabenzoic acid (H4BTEB), was used to design and construct MOFs, hopefully having interpenetrated structures. Combining with 4-connected paddle-wheel Cu2(COO)4 and 8-connected Zr6O4(OH)8(COO)8 clusters, BTEB4− ligand led to two new MOFs, [Cu2(BTEB)(H2O)2] (BUT-43) and [Zr6O4(OH)8(H2O)4(BTEB)2] (BUT-44). As expected, the two MOFs have two-fold interpenetrated framework structures with partitioned channels. BUT-43 contains a rare three-dimensional (3D) 4-connected single network with lvt topology, which then interpenetrates. In BUT-44, each Zr6-based cluster is coordinated with eight BTEB4− ligands to give a single 3D 4,8-connected scu network, which then doubly interpenetrates to give the first example of interpenetrated 4,8-connected Zr(IV)-MOF. Studies on their stability and gas adsorption properties demonstrate that BUT-44 shows higher stability in NaOH solution of pH 10 and 1 M HCl aqueous solution. More interestingly, both MOFs represent good gas adsorption selectivities for C2H2 over CO2 and CH4, suggesting potential application in gas separation.

Tuning Water Sorption in Highly Stable Zr(IV)-Metal–Organic Frameworks through Local Functionalization of Metal Clusters

Water adsorption of metal-organic frameworks (MOFs) is attracting intense interest because of their potential applications in atmospheric water harvesting, dehumidification, and adsorption-based heating and cooling. In this work, through using a hexacarboxylate ligand, four new isostructural Zr(IV)-MOFs (BUT-46F, -46A, -46W, and -46B) with rare low-symmetric 9-connected Zr6 clusters were synthesized and structurally characterized. These MOFs are highly stable in water, HCl aqueous solution (pH = 1), and NaOH aqueous solution (pH = 10) at room temperature, as well as in boiling water. Interestingly, the rational modification of the metal clusters in these MOFs with different functional groups (HCOO-, CH3COO-, H2O/OH, and PhCOO-) enables the precise tuning of their water adsorption properties, which is quite important for given application. Furthermore, all four MOFs show excellent regenerability under mild conditions and good cyclic performance in water adsorption.

Retracted article: In situ formed ternary-based hybrid ink for the fabrication of Cu2ZnSn(S,Se)4 solar cell absorbers

We, the named authors, hereby wholly retract this Journal of Materials Chemistry A article due to data fabrication in Figures 3 and 6. The Raman spectra reported as a CZTSe film in Figure 3b is identical to the Raman spectra reported as CZTSe nanocrystals in Figure 4 of “The synthesis of Cu2Zn(GexSn1−x)Se4 nanocrystals with tunable band gaps”, CrystEngComm, 2013, 15, 6942 [DOI: 10.1039/c3ce40953h]. The UV-vis absorption spectra curves in Figure 6b of films of varying S/Se content are the same curve that has been copied, shifted and pasted within the figure: the purple curve is the copy of the blue curve. An investigation by Dr Yongping Lei (Professor and Chairman of College Council of the College of Materials Science and Engineering, Beijing University of Technology, China) determined that Kai Zong was responsible for these instances of data fabrication. Hao Wang, as his tutor and also corresponding author, is responsible for the duty of supervision and management. Other co-authors accept joint responsibility for the preparation of article. Please allow us to sincerely apologise to all readers and the Editorial Office. Signed: Kai Zong, Yuxiu Sun, Yongzheng Zhang, Hao Wang, Jingbing Liu and Hui Yan, November 2013. Retraction endorsed by Liz Dunn, Managing Editor, Journal of Materials Chemistry A.

Nanocage containing metal-organic framework constructed from a newly designed low symmetry tetra-pyrazole ligand

Abstract 1368-Tetra(1H-pyrazol-4-yl)-9H-carbazole (H4CTP), a tetra-pyrazole ligand with Cs symmetry, has been synthesized based on a carbazole core. A solvothermal reaction of this ligand with NiCl2·6H2O gave a three-dimensional (3-D) metal-organic framework (MOF), [Ni(H4CTP)Cl2]·nS (BUT-41), which crystallized in the cubic space group Pm-3 in spite of H4CPT with a central carbazole core and four peripheral pyrazole rings has low symmetry. The framework of BUT-41 can be regarded as a four-connected 3-D net with the rhr topology when both the organic ligand and the metal center are considered as four-connected nodes. Nanocages with internal diameter of 2 nm are present in the framework of BUT-41, which are formed by interconnecting 12 H4CTP ligands and 20 Ni(II) ions. Each nanocage connects with six adjacent cages through sharing hexagonal windows with diameter over 7 Å, resulting in 3-D intersecting channels of the MOF. Although the tetra-pyrazole ligand is not deprotonated after coordination with the metal ions, powder X-ray diffraction and N2 adsorption experiments reveal that the framework of BUT-41 is rigid and permanently porous with the Brunauer-Emmett-Teller surface area up to 1551 m2 g−1. Furthermore, gas adsorption experiments show that this MOF selectively adsorbs CO2 over N2 and CH4.