An open metal site framework named UTSA-16 was synthesized and modified as a high-capacity adsorbent for reversible CO 2 capture. Partial substitution of intrinsic Co 2+ sites of UTSA-16 with Ni 2+ centres was realized in the molar composition range 0-75% Ni with the aim of increasing CO 2 uptake. Synthesized bimetallic Nix-UTSA-16 (x = 0, 20, 50, 75) materials were characterized using various techniques to assess the influence of chemical composition on CO 2 binding affinity and any subsequent physical change in morphology, crystal size and porosity on the total uptake. Experimental isotherm adsorption studies showed the following trend for CO 2 adsorption capacity employing the Nix-UTSA-16 series: Ni20-UTSA-16 > UTSA-16 > Ni50-UTSA-16 > Ni75-UTSA-16. According to the dynamic breakthrough CO 2 profiles measured for a mixture of CO 2 and CH 4 (15/85 molar ratio), Ni20-UTSA-16 exhibited 2 times the breakthrough time with 1.5 times the loading capacity at 75 Nml min −1 feed flow rate, compared to the parent UTSA-16. In addition, the Ni20-UTSA-16 bimetallic metal-organic framework exhibited lower isosteric heat of adsorption compared to UTSA-16 (ΔH ave = 28.54 versus 46.85 kJ mol −1 ).As a result, more than 95% of its capacity was restored by applying a partial vacuum for only 1 h at room temperature without involving any other timeand energy-consuming regenerative step.