Development of covalent organic polymer (COP) is a potential new class of adsorbent for CO2 separation from natural gas mainly due to their good hydrothermal stability, chemical tuning flexibility and low cost. CO2 and methane adsorption on COP-1 was studied under atmospheric condition (101.3 kPa, 298 K). COP-1 was synthesized via catalyst-free polycondensation of cyanuric chloride and piperazine. The properties of COP-1 were characterized using several analytical methods such as Fourier Transform Infra-Red (FTIR), N2 adsorption and desorption measurement and Field Transmission Electron Microscopy in coupled of Energy Dispersive X-ray Spectroscopy (FESEM-EDS). Reversible CO2 adsorption isotherm on COP-1 reflects low heat of adsorption which is beneficial to energy minimization in adsorbent regeneration process. Furthermore, moderate specific surface area COP-1 (88.5 m2/g) shows about nine times CO2 uptake higher than methane. The highly selective adsorption performance provides a promising insight in application of COP adsorbent for CO2 removal in natural gas field. © 2018 The Authors, published by EDP Sciences.