Zonal activation of molecular carbon dioxide and hydrogen over dual sites Ni-Co-MgO catalyst for CO_(2) methanation:Synergistic catalysis of Ni and Co species

An in-depth mechanism in zonal activation of CO_(2)and H2molecular over dual-active sites has not been revealed yet.Here,Ni-Co-MgO was rationally constructed to elucidate the CO_(2)methanation mechanism.The abundant surface nickel and cobalt components as active sites led to strong Ni-Co interaction with charge transfer from nickel to cobalt.Notably,electron-enriched Coδ-species participated in efficient chemisorption and activation of CO_(2)to generate monodentate carbonate.Simultaneously,plentiful available Ni0sites facilitated H2dissociation,thus CO_(2)and H2were smoothly activated at zones of Coδ-species and Ni0,respectively.Detailed in situ DRIFTS,quasi situ XPS,TPSR,and DFT calculations substantiated a new formate evolution mechanism via monodentate carbonate instead of traditional bidentate carbonate based on synergistic catalysis of Coδ-species and Ni0.The zonal activation of CO_(2)and H2by tuning electron behaviors of double-center catalysts can boost heterogeneous catalytic hydrogenation performance.

Coordination-driven self-assembly of palladium(Ⅱ)-based metallacalixarenes as anion receptors using flexible pyridine-bridged diimidazole ligands

Two types of palladiu m(Ⅱ)-based metallacalixarenes[ML]^(2+)and[ML_(2)]^(2+)have been synthesized through coordination-driven self-assembly from a series of flexible pyridine-bridged diimidazole ligands[2,6-bis((1 H-imidazol-1-yl)methyl)pyridine(L^(1)),2,6-bis((1 H-benzo[d]imidazol-1-yl)methyl)pyridine(L^(2)),2,6-bis((1 H-naphtho[2,3-d]imidazol-1-yl)methyl)pyridine(L^(3))],with palladium(II)-based building blocks[Pd(BF_(4))_(2)(M^(1)-BF_4)and(tmeda)Pd(NO_(3))_(2)(M^(2)-NO_(3))(tmeda=N,N,N',N'-tetramethyl-ethylenediamine)].All complexes were characterized by NMR spectroscopy(^(1)H NMR and^(13)C NMR),mass spectrometry(CSIMS,ESI-HRMS)and elemental analysis.The single crystal X-ray diffraction analysis of[M^(1)L^(2)_2](NO_(3))_(2),[M^(1)L^(3)_2](NO_(3))_(2),[M^(1)L^(3)_2](PF_6)_2 and[M~2 L^(3)](NO_(3))_(2)further confirmed the uniquely single bowl-shape and double bowl-shape structures.The anion binding properties within the metallacalixarenes as receptors were also investigated by NMR titration experiments in DMSO.