화학공학소재연구정보센터
Journal of the American Chemical Society, Vol.142, No.10, 4663-4670, 2020
The Gigantic {Ni36Gd102} Hexagon: A Sulfate-Templated "Star-of-David" for Photocatalytic CO2 Reduction and Magnetic Cooling
Gigantic coordination molecules assembled from a large number of metal ions and organic ligands are structurally and functionally challenging to characterize. Here we show that a hetero-metallic cluster [Ni36Gd102(OH)(132)(mmt)(18)(dmpa)(18)(H(2)dmpa)(24)(CH3COO)(84)(SO4)(18)(NO3)(18)(H2O)30] center dot Br-6(NO3)(6) center dot (H2O)(x) center dot (CH3OH)(y), (1, x approximate to 130, y approximate to 60), shaped like a "Star of David", can be synthesized using a "mixed-ligand" and "sulfate-template" strategy. In terms of metal nuclearity number, 1 is the second largest 3d-4f cluster to date. In the solid state, 1 is porous after removing the lattice guests. The N-2 adsoption experiment reveals that the BET and Langmuir surface areas are 299.8 and 412.0 cm(2) g(-1), respectively. CO2 adsorption at 298 K gives the amount of 45 cm(3) g(-1) for 1. More importantly, 1 is soluble in common organic solvents and exhibits high solution stability revealed by high resolution MALDI-TOF mass spectroscopy, small-angle X-ray scattering (SAXS), and low-dose transmission electron microscopy. The solubility and the potential open metal sites owing to the labile coordinating components prompted us to investigate the photocatalytic properties of 1, which displays high selectivity and efficiency for reduction of CO2 to CO with turnover number and turnover frequency of 29700 and 1.2 s(-1), respectively. These values are higher than most catalysts working under the same conditions, presumably due to the strong Ni-CO2 binding effect. In addition, the large percentage of Gd(III) in 1 leads to a large magnetic entropy change (41.3 J.kg(-1).K-1) at 2.0 K for Delta H = 7 T.