Structural regulation of crystalline Ni/Co-based metal-organic phosphorus materials and the structure-efficiency relationship of their electrochemical performance in supercapacitors

N-(phosphomethyl) amino diethyl acid (pmida) and soluble Ni/Co salts were used to prepare single crystals of isomorphous Ni-based (pmida-Ni) and Co-based (pmida-Co) metal–organic phosphorus complexes were prepared using the hydrothermal method. The structures, morphologies, and electrochemical properties of these complexes were systematically investigated, and the structure–activity relationship was revealed using density functional theory calculations. The results of structural characterization indicated that the materials belong to the orthorhombic Pbca space group, contain 7.7–7.8 Å three-dimensional (3D) connected channels, and have uniform rod-like morphology and uniform elemental distribution. The electrochemical tests showed better comprehensive performance of pmida-Ni: a specific capacitance of 651 F g −1 at 1 A g −1 , a capacitance retention rate of 90% after 10,000 cycles at 5 A g −1 , and a charge transfer resistance of 0.43 Ω. Calculations confirmed a narrow bandgap (0.9604 eV), the low OH − adsorption energy (−0.99 eV), and the better conductivity and electrocatalytic activity of pmida-Ni. The aqueous mixed supercapacitor assembled with pmida-Ni as the positive electrode showed an energy density of 81.25 Wh kg −1 at a power density of 750 W kg −1 and a Coulomb efficiency of 99% after 2000 cycles at 2 A g −1 . Therefore, this study provides an novel design approach for for metal–organic phosphorus complex electrode materials for supercapacitors. • Orthorhombic Pbca Ni/Co organophosphorus single crystal C₅H₁₀LiMNO₈P was hydrothermally made. • DFT revealed that the band gap of pmida-Ni was 0.96 eV and the adsorption energy of OH − was −0.99 eV. • The crystal was fabricated into liquid-state button-type devices with good performance.