Facile synthesis of CuBTC and its graphene oxide composites as efficient adsorbents for CO<inf>2</inf> capture

Abstract

Easily regenerable adsorbents are highly desirable for CO2 capture. In this regard, a modified synthesis method for preparing CuBTC and its graphene oxide (CuBTC@GO) composites as adsorbents is developed using a mixed solvent strategy at 323 K for the first time. The addition of N, N-Dimethylformamide was vital for the crystallization of CuBTC at low temperature by accelerating the nucleation. The newly synthesized CuBTC showed much higher surface area and total pore volume, compared with CuBTC synthesized by conventional method. As a result, the as-synthesized CuBTC showed a CO2 adsorption capacity of 8.02 mmol/g at 273 K, 1 bar, which was 17–90% higher than the reported CO2 capacity of CuBTC prepared by conventional method. The fabrication of CuBTC@GO composites enhanced the CO2 adsorption capacity mainly through the improved porosity and dispersion force. Compared with CuBTC, an improved CO2/N2 selectivity for CuBTC@1%GO was obtained from the binary breakthrough experiments, which is beneficial to practical gas separations. The partition coefficient of CuBTC and CuBTC@GO composite were evaluated at different breakthrough levels, e.g., 5%, 10% and 100%, with an inlet CO2 partial pressure of 0.15 bar. CuBTC@1%GO displayed higher partition coefficient values than CuBTC at all three breakthrough levels. The cyclic adsorption experiments for regenerability evaluation showed that the CO2 adsorption reversibility for CuBTC@1%GO composite could maintain above 90%, while that of CuBTC dropped to less than 74% after five adsorption-desorption cycles. The CuBTC@GO composite would be a promising CO2 capture adsorbent with both high CO2 adsorption capacity and remarkable regeneration performance.