No abstract

Highly efficient electrocatalysts for hydrogen evolution reactions (HER) are crucial for electrochemical water splitting, where high-cost and low-abundance Pt-based materials are the benchmark catalysts for HER. Herein, we report the fabrication of MoP nanoparticles confined in P-doped porous carbon (MoP@PC) via a metal-organic framework-assisted route for the first time. Remarkably, due to the synergistic effects of MoP nanocrystals, P dopant, and porous carbon, the resulting MoP@PC composite exhibits superior HER catalytic activity with an onset overpotential of 97 mV, a Tafel slope of 59.3 mV dec, and good long-term durability, which compares to those of most reported MoP-based HER catalysts. Most importantly, the work opens a new route in the development of high-performance nonprecious HER electrocatalysts derived from MOFs.

Through tuning the length of flexible bis(triazole) ligands and different metal ion coordination geometries, four Wells-Dawson polyoxoanion-based hybrid compounds, [Cu 6(btp) 3(P 2W 18O 62)].3H 2O ( 1) (btp = 1,3-bis(1,2,4-triazol-1-y1)propane), [Cu 6(btb) 3((P 2W 18O 62)].2H 2O ( 2), [Cu 3(btb) 6(P 2W 18O 62)].6H 2O (btb = 1,4-bis(1,2,4-triazol-1-y1)butane) ( 3), and [Cu 3(btx) 5.5((P 2W 18O 62)].4H 2O (btx = 1,6-bis(1,2,4-triazol-1-y1)hexane) ( 4), were synthesized and structurally characterized. In compound 1, the metal-organic motif exhibits a ladder-like chain, which is further fused by the ennead-dentate [P 2W 18O 62] (6-) anions to construct a 3D structure. In compound 2, the metal-organic motif exhibits an interesting Cu-btb grid layer, and the ennead-dentate polyoxoanions are sandwiched by two Cu-btb layers to construct a 3D structure. Compound 3 exhibits a (4 (2).6 (2).8 (2)) 3D Cu-btb framework with square and hexagonal channels arranged alternately. The hexa-dentate polyoxoanions incorporate only into the hexagonal channels. In compound 4, there exist two sets of (6 (1).10 (2)) 2(6 (1).8 (2).10 (3)) 3D Cu-btx frameworks to generate a 2-fold interpenetrated structure into which the penta-dentate polyoxoanions are inserted to construct a 3D structure. The structural analyses reveal that the length of flexible bis(triazole) ligands and metal ion coordination geometries have a synergic influence on the structures of this series. To our knowledge, they have the highest connectivity for the Wells-Dawson polyoxometalate coordination polymers to date.

Through tuning the spacer length of flexible bis(triazole) ligands, three Keggin anion-based coordination polymers with different dimensionalities, [Cu4(H2O)4(bte)2(HPMoVI 10MoV 2O40)]·2H2O (1) (bte = 1,2-bis(1,2,4-triazol-1-yl)ethane), [Cu(btb)][Cu2(btb)2(PMo12O40)] (2) (btb = 1,4-bis(1,2,4-triazol-1-y1)butane), and [Cu5(btx)4(PMoVI 10MoV 2O40)] (3) (btx = 1,6-bis(1,2,4-triazol-1-y1)hexane), were synthesized and structurally characterized. Compound 1 exhibits a ladder-like chain, in which the polyoxometalate (POM) anions act as the “middle rails” of the ladder. The bte ligand with shortest spacer length acts as not only the bridging linker but also the chelator, which terminates the dimensional extension. Compound 2 exhibits a 2D POM-based framework, containing POM/Cu/btb grid-like layers. In compound 3, there exist three sets of (123)(121)2 2D Cu-btx frameworks to generate a 3-fold interpenetrating structure, into which the hexadentate POM anions are inserted to construct a 3D structure. The structural analyses reveal that the spacer length of flexible bis(triazole) ligands has influence on the dimensionality of these compounds.