Developing energy-efficient alternatives for methane (CH4) purification from natural gas and methane capture of coal-mine gas is of great significance and challenge in the chemical industry. Herein, we report a robust nickel-based metal-organic framework (MOF), Ni-BPZ, featuring one-dimensional (1D) rhombic channels decorated with abundant pyrazole rings. Ni-BPZ exhibits excellent separation performance toward both C2H6/CH4 and CH4/N2 binary mixtures. The C2H6/CH4 selectivity of Ni-BPZ is high, up to 50.2, exceeding those of most MOF adsorbents reported, and it simultaneously possesses a remarkable C2H6 uptake of 2.46 mmol/g at 298 K and 0.1 bar. The CH4/N2 selectivity of Ni-BPZ reaches 6.6, and its high CH4 uptake is 1.56 mmol/g, which is also superior to most high-performance CH4 adsorbents. The molecular simulation reveals that the uniform 1D rhombic channels with abundant pyrazole rings provide a high density of potential adsorption sites for efficient C2H6/CH4 and CH4/N2 separations.