Structural Characterization of Transition-Metal Carboxyethanephosphonates as Precursors of Electrocatalysts

Phosphorus-containing coordination polymers (CPs) are considered as one of the most promising precursors of materials alternative to the highly expensive commercial catalysts (Pt, Ru and Ir) used in polymeric fuel cells and electrolysers. Among them, metal phosphonates, a subtype of coordination polymers, are attractive precursors due to their great chemical and structural diversity. Indeed, the possibility of containing in their compositions electrocatalytically active transition metals in combination with other elements (N, C, P, S, etc…) may enhance the electrochemical properties of the resulting materials after pyrolytic treatments. In this work, we report the synthesis and crystal structures of several transition-metal phosphonates derived from the ligand phosphonopropionic acid (PPA). Solids with compositions AxB1-x[O3PCH2CH2COOH]2·nH2O (A2+ and B2+= Mn, Fe, Co, and Ni; 0≤ x≤ 2 and n= 0, 2) were prepared by thermal-drying or mechano-assisted synthesis and, depending on the metal cation and water content, different layered frameworks were obtained, which have been solved from laboratory powder X-ray diffraction data. All obtained solids were pyrolyzed under 5%H2-Ar atmosphere, at different temperatures, in order to obtain transition-metal phosphides (MxP) which have been studied as possible electrocatalysts toward Oxygen Evolution Reaction (OER), Oxygen Reduction Reaction (ORR) and Hydrogen Evolution Reaction (HER). Correlations between the crystalline structures of the precursor phases with the electrocatalytic activity of the pyrolyzed derivatives will be discussed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Proyectos nacionales MAT2016-77648-R y PID2019-110249RB-I0

Synthesis and antibacterial activity of bimetallic carboxyphosphonates

As a class of coordination polymers (CPs), metal phosphonates (MPs) are constructed by coordination bonds connecting metal sites and phosphonate (RPO3 2−) ligands, where the metal sites are dispersed uniformly at the atomic level. The synthetic chemistry of phosphonates is well developed, so phosphonic acids can be obtained through simple, well-known reactions, enabling the synthesis of phosphonate derivatives of non-steroidal anti-inflammatory drugs (NSAIDs) to be carried out. We report here, general characteristics of a new series of isostructural compounds resulting from the combination of the multifunctional R,S-hydroxyphophonoacetic acid (HPAA) with transition metal ions, AgMII[HO3PCH(OH)COO] (MII= Co or Zn), AgMHPAA. Both compounds were synthesized under hydrothermal conditions and their crystal structures were solved from single crystal diffraction data. The antibacterial activity of AgZnHPAA and AgCoHPAA was evaluated using three different bacterial strains: Staphylococcus aureus (NCIMB 6571), Escherichia coli K12 W-T (W1485 Cardiff Collection) and Pseudomonas aeruginosa (NCIMB 8295). Preliminary results regarding their antibacterial properties will be presented and discussed.Universidad de Málaga. Campus de Excelencia Interna Andalucía Tech. Proyectos nacionales MAT2016-77648-R y PID2019-110249RB-I00ciona

Synthesis, structural characterization and electrocatalytic properties of cobalt phosphides and pyrophosphates derived from glyphosine

Póster presentado en el XXX Simposio del GE3CMetal phosphonates (MPs), a subclass of coordination polymers, result from the bonding of phosphonic acids (RPO32-) with metal ions, giving rise to an uniformly dispersion of the metal sites at the atomic scale. This characteristic allows the preparation of metal-phosphorous-based nano-carbon composites by a simple one-step pyrolysis, what makes them very attractive precursors of Non-Precious Metal Catalysts (NPMCs). Herein, we report the synthesis, characterization and electrochemical properties of three cobalt(II) coordination polymers derived from the glycine-N,N-bis(methylenenphosphonic acid) (BPMGLY), with formula [Co(C4H9O8NP2(H2O)2]·nH2O (n=0, 2). In contrast with the zero-dimensional structure of [Co(C4H9O8NP2(H2O)2]·2H2O (Co-BPMGLY-I), the two new polymorphs synthesized, Co(C4H9O8NP2(H2O)2 (Co-BPMGLY-II and Co-BPMGLY-III), whose structures have been solved from powder diffraction data, show two-dimensional frameworks with different connectivity between the Co2+ ions and the ligand within the sheets. These MPs were used as precursors of NPMCs by pyrolyzing them under 5%-H2/Ar at different temperatures. The electrochemical behavior of the resulting compounds, mainly crystalline cobalt pyrophosphates and/or phosphides, is fully studied regarding to the Oxygen Evolution and Reduction Reactions (OER and ORR, respectively) as well as Hydrogen Evolution Reaction (HER). Cobalt phosphide (CoP) derived from Co-BPMGLY-I displayed the best results, showing an overpotential of 156 mV for HER.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Proyectos nacionales MAT2016-77648-R y PID2019-110249RB-I0

New Multifunctional Zirconium(IV) Phosphonates Derivativesas Proton Conductors and Catalysts

Coordination polymers based in phosphonic acid display a wide range of metalcoordination modes. Moreover, the existence of acidic P-OH groups in their structure, as well as of others functionalized organic group such as carboxylic or amino groups, and the presence of coordination and/or lattice water molecules favors the formation of hydrogen bond networks, make them appropriate materials as proton conductors and, therefore, attractive for proton exchange membranes of fuel cells or electrolyzers.The current interest in metal phosphonates, lies in their properties, such as high chemical and thermal stability and high insolubility. In addition, zirconium phosphonates have also been studied for specific purpose such as catalysis, ion exchange and intercalation processes, so on. In this work, we reported the synthesis, characterization and structural determination of three new zirconium phosphonates derived from the phosphonic acids: Zr-PNA (PNA = 5-(dihydroxyphosphoryl) nicotinic acid), Zr-BTMP (BTMP = 1,2,3-[phenelyenetris(methylene)]tris-phosphonic acid) and Zr-PiPthA (PiPthA = 5-(dihydroxyphosphoryl)-isophthalic acid). All zirconium derivatives were synthesized under hydrothermal conditions at 80 ºC in the presence of HF as mineralizing agent. The crystal structures of Zr-PNA and Zr-BTMP have been solved from powder X-ray diffraction data and both solid crystallize in the monoclinic system. Zr-PNA shows a 1D structure formed by chains of ZrO4F2 octahedra bridged by the phosphonates groups of the ligand, while Zr-BTMP exhibits a 3D framework formed by double chains of isolated ZrO6 octahedra bridged by the different phosphonates groups of the ligand. Compound Zr-PiPthA,crystallizes in an orthorhombic unit cell (a = 21.9306 Å, b = 16.6169 Å, c = 3.6462 Å). Their structural features, proton conductivity and ion exchange properties as well as their catalytic behavior toward the one-pot transformation of furfural to other bio-products reaction will be discussed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Proyectos I+D+i nacionales MAT2016-77648-R y PID2019-110249RB-I00 del MICINN. Grupo de investigación FQM-113 y Proyecto I+D+i de la Junta de Andalucía PAIDI2020- DOC_00272