[Co₃(μ₃-O)]-Based Metal-Organic Frameworks as Advanced Anode Materials in K- and Na-Ion Batteries

A new metal-organic framework {(Me₂NH₂)₂[Co₃(μ₃-O)(btb)₂(py)(H₂O)]·(DMF)₂(H₂O)₂}_n (Cobtbpy) was solvothermal synthesized (H₃btb = 1,3,5-tri(4-carboxylphenyl)benzene, py = pyridine, DMF = N,N-dimethylformamide). Cobtbpy shows a (3,6)-connected rtl 3D network with a point symbol of (4·6²)₂(4²·6¹⁰·8³) based on the [Co₃(μ₃-O)] clusters. The obtained Cobtbpy has stable, accessible, dense active sites and can be applied in the potassium- and sodium-ion batteries. Through mixing with single-walled carbon nanotubes, the prepared composite anode material Cobtbpy-0.9 achieved a high reversible capability, delivering 416 mAh/g in the potassium-ion batteries and 379 mAh/g in the sodium-ion batteries at 0.05 A/g. The outstanding properties of Cobtbpy-0.9 in the batteries demonstrated that this MOFs-based carbon composite is a highly desirable electrode material candidate for high-performance potassium- and sodium-ion batteries.