Facile "Green" Aqueous Synthesis of Mono- and Bimetallic Trimesate Metal-Organic Frameworks

[EN] Various isoreticular monometallic (Co2+, Ni2+, Cu2+, and Zn2+) and bimetallic (Co-Ni, Co-Zn, Mn-Ni) trimesate MOFs have been prepared by a fast (10 min) and green synthesis method from aqueous solutions, at room temperature and ambient pressure. A combined XRD and SEM/EDX analysis clearly revealed bimetallic compounds form true solid solutions rather than a simple physical mixture of pure-phase monometallic compounds. Moreover, a detailed evaluation of the evolution of cell parameters with the composition provides strong evidence indicating a preferential occupation of one crystallographic position (bidentate terminal sites) by Co2+ (or Mn2+) ions. This leads to a precise and predictable array of metal ions in the framework, which can be finely tuned by changing the overall composition of the bimetallic MOF. Implications are envisaged in the design and catalytic properties of well-defined single-site catalysts.This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 641887 (project acronym: DEFNET) and the Spanish Government through projects MAT2017-82288-C2-1-P and Severo Ochoa (SEV-2016-0683). The Microscopy Service of the Universitat Politecnica de Valencia is gratefully acknowledged for the electron microscopy measurements.Nowacka, AE.; Briantais, P.; Prestipino, C.; Llabrés I Xamena, FX. (2019). Facile "Green" Aqueous Synthesis of Mono- and Bimetallic Trimesate Metal-Organic Frameworks. Crystal Growth & Design. 19(9):4981-4989. https://doi.org/10.1021/acs.cgd.9b00237S4981498919

Selective Aerobic Oxidation of Cumene to Cumene Hydroperoxide over Mono- and Bimetallic Trimesate Metal Organic Frameworks Prepared by a Facile Green Aqueous Synthesis

"This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Sustainable Chemistry & Engineering, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acssuschemeng.8b06472"[EN] Co-Ni and Mn-Ni bimetallic trimesate MOFs prepared by a fast aqueous synthesis method are excellent and reusable catalysts for the selective aerobic oxidation of cumene to cumene hydroperoxide (CHP). Isolation of Co2+ (or Mn2+) in an inert Ni-BTC framework is a good strategy to optimize CHP selectivity above 90%: since only Co2+ sites catalyze CHP decomposition, a drop of the CHP selectivity is observed as the cobalt content in the bimetallic MOF increases. The statistical probability of having isolated Co2+ sites is calculated as a function of the total cobalt content of the bimetallic compound, assuming homogeneous distribution of Co2+ ions in the Ni-BTC framework and preferential occupation of terminal sites. Thus, in our best sample, with a Co:Ni ratio of 5:95, 73% of the total Co2+ ions are isolated so that CHP decomposition/overoxidation processes at the surface of the catalyst are not likely to occur before CHP desorption. This can explain the excellent CHP selectivity (91%) attained over this material. This "site isolation" effect is further supported by similar findings on Mn-Ni bimetallic compounds.This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 641887 (project acronym: DEFNET) and the Spanish Government through projects MAT2017-82288-C2-1-P and Severo Ochoa (SEV-2016-0683).Nowacka, AE.; Briantais, P.; Prestipino, C.; Llabrés I Xamena, FX. (2019). Selective Aerobic Oxidation of Cumene to Cumene Hydroperoxide over Mono- and Bimetallic Trimesate Metal Organic Frameworks Prepared by a Facile Green Aqueous Synthesis. ACS Sustainable Chemistry & Engineering. 7(8):7708-7715. https://doi.org/10.1021/acssuschemeng.8b06472S770877157

Cubic lead perovskite PbMoO3 with anomalous metallic behavior

A previously unreported Pb-based perovskite PbMoO$_3$ is obtained by high-pressure and high-temperature synthesis. This material crystallizes in the $Pm\bar{3}m$ cubic structure at room temperature, making it distinct from typical Pb-based perovskite oxides with a structural distortion. PbMoO$_3$ exhibits a metallic behavior down to 0.1 K with an unusual $T$-sub linear dependence of the electrical resistivity. Moreover, a large specific heat is observed at low temperatures accompanied by a peak in $C_P/T^3$ around 10 K, in marked contrast to the isostructural metallic system SrMoO$_3$. These transport and thermal properties for PbMoO$_3$, taking into account anomalously large Pb atomic displacements detected through diffraction experiments, are attributed to a low-energy vibrational mode, associated with incoherent off-centering of lone pair Pb$^{2+}$ cations. We discuss the unusual behavior of the electrical resistivity in terms of a polaron-like conduction, mediated by the strong coupling between conduction electrons and optical phonons of the local low-energy vibrational mode.Comment: 5 pages, 5 figure