3D graphene-like zeolite-templated carbon with hierarchical structures as a high-performance adsorbent for volatile organic compounds

Dynamic adsorption studies of vaporous benzene (3000 ppm) on a hierarchically mesoporous/microporous beta zeolite-templated carbon (HBTC) was compared to those of commercial activated carbon (AC) and solely microporous beta zeolite-templated carbon (BTC). The BTC had periodic micropores with a narrow distribution of 1 nm in size and a high micropore surface area of ~2870 m² g⁻¹, thereby showing a much higher dynamic adsorption capacity (653 mg g⁻¹) for benzene than that exhibited by the AC (264 mg g⁻¹). Nevertheless, the BTC exhibited a lower breakthrough time (3.26 mg) for benzene than that shown by the AC (4.9 mg) owing to severe diffusion constraints. The diffusion problem can be solved by introducing mesoporosity into microporous BTC to form a hierarchically mesoporous/microporous structure. Isosteric heat and benzene diffusivity results indicated the strong affinity and facile diffusion exhibited by the hierarchical BTC, which were attributed to the graphitic nature of the carbon framework, uniform micropores, and hierarchically mesoporous/microporous structures. Therefore, the HBTC exhibited a benzene breakthrough time of 11.4 mg and a dynamic adsorption capacity of 472 mg g⁻¹ (100% breakthrough) that was larger than those of commercial AC. Furthermore, the adsorption capacity and partition coefficient (PC) of the tested adsorbents were evaluated at 10% breakthrough. Among all tested carbons, HBTC exhibited the best performance for benzene capture with adsorption capacity of 332 mg g⁻¹ and PC value of 0.140 mol Kg⁻¹ Pa⁻¹. The effects of adsorption temperature and relative humidity on the benzene adsorption capacities of HBTC and BTC were also explored. Furthermore, desorption and subsequent regeneration studies demonstrated that the adsorption capacity of HBTC can be completely restored by heat treatment. These findings indicate that HBTC is a promising candidate for VOC adsorption that can replace the currently employed commercial AC.