Heterogeneity within a Mesoporous Metal-Organic Framework with Three Distinct Metal-Containing Building Units.

Materials built from multiple constituents have revealed emerging properties that are beyond linear integration of those from single components. We report a mesoporous metal-organic framework made from three geometrically distinct metal-containing secondary building units (SBUs) as a result of topological induction. The combinations of the Cu-based triangular, Zn-based octahedral, and Zn-based square pyramidal SBUs have created four types of cages in the network, despite that only one organic linker pyrazolecarboxylate was used. The longest distance for molecules maneuvering inside the largest cage is 5.2 nm. Furthermore, the complex and diversified pore environments allow the installation of various new functionalities in the framework as well as the expedited Ag nanoparticle formation in the pores. As presented in the molecule movement diagram, the crystal has provided specific arrangements of cages and apertures with distinct chemical features for guests transporting between the pores.

Ordered vacancies and their chemistry in metal-organic frameworks.

Vacancies are common in solid materials, but it remains a challenge to introduce them at specific locations with controlled distributions. Here we report the creation of ordered metal vacancies and linker vacancies in a cubic metal-organic framework (MOF) based on Zn(II) and pyrazolecarboxylic acid by removing a quarter of the metal ions and half of the linkers. The MOF with ordered vacancies shows increased pore size, thus allowing large dye molecules to fit in the pores. Furthermore, by filling the vacancies with new metals and new linkers, eight new single-crystalline MOFs with multicomponents in absolute order are introduced. The capability of performing stepwise elimination and addition reactions systematically in extended solids without destroying the structural integrity has generated complex MOF structures which otherwise cannot be made.

Coupled MoO3-x@CoP heterostructure as a pH-universal electrode for hydrogen generation at a high current density.

Developing high-performance and low-cost self-supporting electrodes as pH-universal electrocatalysts for the hydrogen-evolution reaction (HER) and realizing high-quality hydrogen production at a high current density are highly desirable, but are hugely challenging. We created a self-supporting electrode with a coupled hierarchical heterostructure by simple electrodeposition followed by sulfurization. It comprised oxygen-deficient molybdenum oxide (MoO3-x) and cobalt phosphide (CoP) on nickel foam (NF), which represented a highly active pH-universal electrocatalyst for the HER at a high current density. Benefiting from a plethora of catalytic active sites, improved interfacial charge transfer, and strong electronic interaction, this type of MoO3-x@CoP/NF electrode delivered a superior catalytic performance. Overpotentials of only 100 mV, 135 mV, and 400 mV were needed to realize a high current density of 1 A cm-2 in alkaline, acid and neutral media, respectively, which were superior to those of most other well-developed materials based on non-noble metals. Our experimental work demonstrates the synergistic advantages of a MoO3-x@CoP heterostructure for improving the intrinsic catalytic performance but also paves a new path for the rational design of advanced electrodes for hydrogen generation in a wide range of pH conditions.

Highly efficient electrochemical reduction of carbon dioxide to formate on Sn modified Bi2O3 heterostructure.

In this work, Sn species are deposited onto the surface of a Bi2O3 material by a facile disproportionated reaction and the prepared catalyst shows a superior electrocatalytic performance towards CO2 reduction. The deposition of Sn atoms can donate electrons to the Bi2O3 material and increase its electrical conductivity. The SnM-Bi2O3 catalyst with the optimal Sn content delivers a high faradaic efficiency of 95.8% at -1.0 V for formate production. In addition, the partial current density of formate can reach 41.8 mA cm-2. The SnM-Bi2O3 catalyst also exhibits superior stability towards long-term electrolysis. The modification of Sn species not only helps to stabilize the reaction intermediate but also inhibits the hydrogen evolution reaction (HER) pathway, achieving the synergetic enhancement of catalytic activity.

Highly efficient heterogeneous photo-Fenton BiOCl/MIL-100(Fe) nanoscaled hybrid catalysts prepared by green one-step coprecipitation for degradation of organic contaminants.

An excellent heterojunction structure is vital for the improvement of photocatalytic performance. In this study, BiOCl/MIL-100(Fe) hybrid composites were prepared via a one-pot coprecipitation method for the first time. The prepared materials were characterized and then used as a photo-Fenton catalyst for the removal of organic pollutants in wastewater. The BiOCl/MIL-100(Fe) hybrid exhibited better photo-Fenton activity than MIL-100(Fe) and BiOCl for RhB degradation; in particular, the hybrid with 50% Bi molar concentration showed the highest efficiency. The excellent performance can be ascribed to the presence of coordinatively unsaturated iron centers, abundant Lewis acid sites, fast H2O2 activation, and efficient carrier separation on BiOCl nanosheets due to the high charge carrier mobility of the nanosheets. The photo-Fenton mechanism was studied, and the results indicated that ˙OH and h+ were the main active species for organic pollutant degradation. The coprecipitation-based hybridization approach presented in this paper opens up an avenue for the sustainable fabrication of photo-Fenton catalysts with abundant coordinatively unsaturated metal centers and efficient electron-hole separation capacity.

A triptycene-based porous hydrogen-bonded organic framework for guest incorporation with tailored fitting.

A hydrogen-bonded organic framework (HOF) was constructed by avoiding potential π-π stacking of building blocks with robust and non-coplanar triptycene-based modules. The tailored-fitting interactions were demonstrated by the adsorption of fullerene with a concentration enrichment of ∼420 times in the pores.

Metal-organic frameworks as cathode materials for Li-O2 batteries.

Metal-organic frameworks (MOFs) with open metal sites enrich the population of O2 in the pores significantly and assist the Li-O2 reaction when employed as a cell electrode material. A primary capacity of 9420 mA h g(-1) is achieved in a cell with Mn-MOF-74; more than four times higher than the value obtained in a cell without an MOF.