Metal–organic frameworks (MOFs) have diverse applications involving the storage, separation and sensing of weakly interacting, high-purity gases. Exposure to impure gas streams and interactions with corrosive and coordinating gases raises the question of chemical robustness; however, the factors that determine the stability of MOFs are not fully understood. Framework materials have been previously categorized as either thermodynamically or kinetically stable, but recent work has elucidated an energetic penalty for porosity for all these materials with respect to a dense phase, which has implications for the design of materials for gas storage, heterogeneous catalysis and electronic applications. In this Review, we focus on two main strategies for stabilization of the porous phase — using inert metal ions or increasing the heterolytic metal–ligand bond strength. We review the progress in designing robust materials for the capture of coordinating and corrosive gases such as H2O vapour, NH3, H2S, SO2, nitrogen oxides (NOx) and elemental halogens. We envision that the pursuit of strategies for kinetic stabilization of MOFs will yield increasing numbers of robust frameworks suited to harsh conditions and that short-term stability towards these challenging gases will be predictive of long-term stability for applications in less demanding environments. Metal–organic frameworks, when evacuated, are metastable with respect to a dense phase of the same components. Here, we review methods for kinetic stabilization of the porous phase and discuss progress in designing stable frameworks for the capture of corrosive and coordinating gases.

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Kinetic stability of metal–organic frameworks for corrosive and coordinating gas capture

Gd-modified MnOx for the selective catalytic reduction of NO by NH3: The promoting effect of Gd on the catalytic performance and sulfur resistance

MOFs-derived Cu3P@CoP p-n heterojunction for enhanced photocatalytic hydrogen evolution

Preparation of MOFs and MOFs derived materials and their catalytic application in air pollution: A review

Monometallic and bimetallic MOF-74-M (M = Mn, Co, Ni, Zn, MnCo, MnNi, and MnZn) catalysts were prepared by the solvothermal method for NH3-SCR. XRD, BET, SEM, and EDS-mapping tests indicate the successful synthesis of the MOF-74-M catalyst with uniform distribution of metal elements and large specific surface area, and the morphology is almost hexagonal. Adding Mn element to a single-metal catalyst can enhance activity, which is mainly because of the existence of various valence states of Mn so that it has excellent redox properties; the catalytic activity of water and sulfur resistance tests showed that the catalytic activity of MOF-74-M increases after adding a proper amount of SO2, mainly because of the increase in acidic sites. In situ DRIFTS results indicate that the low-temperature range of MOF-74-MnCo and MOF-74-Mn is dominated by the E-R mechanism and the high-temperature range is dominated by the L-H mechanism. The entire temperature range of MOF-74-Zn is dominated by the L-H mechanism.

MOF-74-M (M = Mn, Co, Ni, Zn, MnCo, MnNi, and MnZn) for Low-Temperature NH3-SCR and In Situ DRIFTS Study Reaction Mechanism.

The novel Cu-MOF-74 materials were synthesized with various cosolvents at different temperatures by a solvent-thermal method and then developed as NO removal catalysts for low temperature selective catalytic reduction (SCR) with NH3. The physicochemical properties of catalyst samples were characterized by multiple techniques, such as N2 adsorption–desorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). The effects of cosolvent on the catalyst performances were systematically investigated. It was found that Cu-MOF-74-iso-80 catalyst showed the highest NH3-SCR activity, giving 97.8% NO conversion and 100% N2 selectivity at 230 °C. BET test results suggested that Cu-MOF-74 showed a larger specific surface area. Stronger NH3 adsorption ability was found, which could be beneficial for SCR at low temperature. The catalyst also showed better water resistance performance. The adverse effect of H2O added intermitt...

Effect of Cosolvent and Temperature on the Structures and Properties of Cu-MOF-74 in Low-temperature NH3-SCR

In this study, the MnOx-FeOy hollow nanospheres with solid solution structure were prepared by supercritical antisolvent (SAS) process. The average particle size was about 50 nm, and average pore diameter was 7 nm. By applying the SAS method, novel nonsupported MnOx-FeOy catalysts with a Mn/Fe mass ratio of 1:1 showed rather high selective catalytic reduction activity and broad active temperature window. The NOx conversion rate reached 97% at 220 °C, and maintained above 92% from 180 to 260 °C. The experiment results showed that iron doping could cause the apparent change of MnOx morphology and structure, which enhanced the oxidative ability of manganese species and increased surface active oxygen species. Meanwhile, compared with traditional methods, the SAS process could efficiently enhance the interaction between manganese and iron, and produce smaller size and larger pore volume nanoparticles with more active sites on the surface.

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Study on MnOx-FeOy composite oxide catalysts prepared by supercritical antisolvent process for low-temperature selective catalytic reduction of NOx

The invention relates to a method for preparing nanoscale composite Ce-Zr oxide particles by supercritical antisolvent (SAS) technique. The method comprises the following steps: dissolving a Ce salt and a Zr salt in a solution; separating out the soluble salts of the Ce and Zr in a manner of uniformly-dispersed nanoparticles through the antisolvent effect of supercritical fluids to obtain the nanoscale precursor particles of the supercritical antisolvent; and baking the precursor to obtain the nanoscale composite Ce-Zr oxide particles. The SAS technique is a pure physical process so as to obviate the complex steps, such as washing and drying, of the conventional coprecipitation method, and has the advantages of mild operation condition, easily controlled process, small particle size, uniform size distribution, uniform distribution of each composite component, repeated use of CO2 and solvent, environmental protection, etc.

Method for producing cerium-zirconium nanocomposite oxide fine particle with supercritical anti-solvent technology

CeO2–ZrO2–Al2O3 ternary oxides as a support for CO oxidation was synthesized successfully via supercritical anti-solvent (SAS) precipitation using CO2 as the anti-solvent and methanol as the solvent. It was found that the CeO2–ZrO2–Al2O3 fabricated by SAS precipitation (CZA1) had superior resistance to sintering compared to the traditional co-precipitation method (CZA2). Meanwhile, the oxygen storage/release rate of CAZ1 was almost 1.5 times higher than that of CZA2 and the total oxygen storage capacity (OSC) of CAZ1 was almost twice as high as CZA2. The interactions between the Pd and the CeO2–ZrO2–Al2O3 support were stronger for the support synthesized by SAS precipitation. The conversion of CO oxidation of Pd/CZA1 was even better than that of Pd/CZA2, especially at high GHSV.

Yonghui Li

Papers

Effect of Cosolvent and Temperature on the Structures and Properties of Cu-MOF-74 in Low-temperature NH3-SCR

Study on MnOx-FeOy composite oxide catalysts prepared by supercritical antisolvent process for low-temperature selective catalytic reduction of NOx

Method for producing cerium-zirconium nanocomposite oxide fine particle with supercritical anti-solvent technology

CeO2–ZrO2–Al2O3 Ternary Oxides Synthesized via Supercritical Anti-Solvent and as a Support for Pd Catalyst for CO Oxidation