Gas separation method using adsorbent

A gas separation method for separating a specific component gas from a mixed gas using an adsorbent, comprising:

• (1) a contact step of bringing a mixed gas into a vessel to contact, at a first pressure, said mixed gas with an adsorbent with respect to which a specific component gas has differences between its adsorption and desorption isotherms;
• (2) a decompression step of decompressing said mixed gas in said vessel to a second pressure, which is lower than the first pressure and which is within a range of pressures at which there are differences between the adsorption and desorption isotherms;
• and
• (3) a desorption step of causing adsorbed matter to detach by placing the adsorbent at a third pressure, which is lower than said second pressure and which is outside of said range of pressures at which there are differences between the adsorption and description isotherms and/or by heating the adsorbent,
• wherein the adsorbent is an organic metal complex represented by general formula (1):
• M·L3 (1),
• wherein M is a metal atom;
• and L is a ligand comprising substituted or unsubstituted cyclic groups A and B, where a substituent on the cyclic groups A and B is independently selected from the group consisting of a halogen atom, a nitro group, and a trialkysilyl group, wherein the alkyl group is, independently, a linear or branched alkyl group having 1 to 8 carbon atoms.