Understanding the KOH activation mechanism of zeolitic imidazolate framework-derived porous carbon and their corresponding furfural/acetic acid adsorption separation performance

Efficient separation of furfural from an acid-containing aqueous solution is a critical step in the furfural production process. Zeolitic imidazolate framework (ZIF)-derived porous carbons with acid resistance and tunable surface chemistry/pore structure are promising adsorbents for the separation of organic compounds from acid-containing aqueous solutions. However, little attention has been given to establish the trend of distribution of micropores and mesopores in the chemical activation of ZIF-derived porous carbon, which directly affects the adsorption performance. Herein, we investigated the relationship between the distribution of micropores and mesopores and the N species content/type in the chemical activation of the N-doped ZIF-8-derived porous carbon, and the KOH activation mechanism was proposed. The intermediates K 2 CO 3 /K 2 O reacted with the C species of NC ZIF-8 1000C with a low N content, the CO was formed, and the structural deformation was not substantial, which is beneficial for the construction of abundant and larger micropores (10–20 Å), and a few mesopores (20–30 Å). While the reaction of the intermediate K 2 CO 3 /K 2 O with the higher-reactivity C–N species (pyridine and pyrrolic) of NC ZIF-8 800C with a high N content resulted in the formation of the intermediate product KOCN and decomposition product CO and NO, and the structural deformation was substantial, which led to the formation of abundant and larger mesopores (30–60 Å). Furthermore, the furfural (5.0 wt.%) static adsorption on the designed NC ZIF-8 1000C-700A with the abundant micropores is 1189.8 mg g −1 , and the selectivity of furfural/acetic acid mixture (5.0/2.0 wt.%) is 91.5, which exceeds that of traditional adsorbents.