4-Connected Cobalt-Based 3D Framework with a High Affinity for Acetylene.

A 3D framework, [Copip]·(H2O)0.3 (NbU-11), was synthesized by a hydrothermal method. Although there are no open metal sites and Lewis basic adsorption sites, gas adsorption measurements and ideal adsorbed solution theory (IAST) calculations all reveal that NbU-11 shows a high affinity for acetylene (C2H2). Remarkably, the adsorption selectivity values predicted by IAST for equimolar binary C2H2/CH4 and C2H4/CH4 mixtures are up to 175.8 and 42.8 at 295 K and 1 bar, respectively. Moreover, gas mixture breakthrough tests confirm that NbU-11 exhibits moderately high separation selectivities for C2H2/CO2 and C2H2/C2H4 as well as excellent separation selectivities for C2H2/CH4 and C2H4/CH4. Such an excellent performance makes NbU-11 a promising adsorbent for C2H2 capture.