N-doped porous carbons (NPCs) are promising adsorbents for carbon capture and sequestration. Herein we prepare a series of NPCs derived from triazine-based hyper-cross-linked polymers and tune the porosity and nitrogen content by carbonization temperature and activator. The NPCs prepared at 800 degrees C using KOH as the activator has the highest Brunauer-Emmett-Teller surface area (3542m(2)/g) while the NPCs prepared at 700 degrees C using ZnCl2 as the activator possesses the highest N content (7.27 wt%). The CO2 adsorption indicates that the NPCs prepared at 700 degrees C with KOH holds the highest CO2 uptake (240 mg/g) while the NPCs prepared at 700 degrees C with ZnCl2 owns the highest CO2/N2 selectivity (42.6). The CO2 uptake at 1.0 bar depends linearly on the cumulative supermicropore volume (d < 1.2 nm) (V-super), while nitrogen content plays an important role for CO2 uptake at a low pressure (0.1 bar). CO2/N-2 selectivity is mainly related to V-super versus the cumulative micropore volume (d < 2 nm) (V-micro) and nitrogen content, especially pyridinic N and quaternary N. These porous carbons exhibit moderate isosteric heat of adsorption (19.3-28.3 kJ/mol), can be completely regenerated, and show excellent recycling performance. Our study provides promising porous carbons for CO2 capture and affords effective guideline for designing porous materials with an improved CO2 capture.