## 1 Introduction  
Volatile organic compounds (VOCs) are a wide array of hydrocarbon-based gases and vapors that are known as one of the major contributors to air pollution. VOCs can be found in various industrial exhausts including, but not limited to, transportation, chemical industries, petrochemical plants, and petroleum refineries [1]. VOCs' high vapor pressure, low boiling point, and strong reactivity contribute to their photochemical reaction in the atmosphere [2]. Many negative impacts of VOCs on human health and the environment, such as their contribution to the depletion of the ozone layer, photochemical ozone formation in the tropospheric layer, global greenhouse effect, and contribution to the formation of fine particulate matter (PM\({}_{2.5}\)), have been reported [3; 4]. Some VOCs are known carcinogenic, mutagenic, and neurotoxic chemicals [5]. Due to the negative effects of VOCs on humans and the environment, and the fact that their concentration in the atmosphere is increasing (e.g., as a result of industrialization), environmental regulations aim to control and decrease the emission of VOCs into the environment. The Goteborg Protocol recommendation is to decrease the world's VOC emission by 50% by 2020 compared to the base year of 2000 [4; 6]. Accordingly, in recent years, great efforts have been made to develop new and more efficient techniques for VOC abatement from emission sources. A wide array of physicochemical technologies, such as thermal and catalytic oxidation, photocatalytic oxidation [7], biological degradation [8; 9], condensation, adsorption, and absorption [3], have been used for capturing VOCs from industrial exhausts [10]. In comparison to other air pollution control technologies, adsorption-based technologies are being considered as simple, capable to manage multicomponent pollutants, efficient and cost effective process that can be used for capturing and recovering VOCs at different concentrations [11; 12]. While adsorption can occur at all solid-gas interfaces, however, the capacity of adsorbents to capture the adsorbate molecules depends on the different characteristics of adsorbents including specific surface area, pore size distribution [13; 14], pore volume, particle size, presence of functional groups, and a preferential affinity for the target adsorbate [15]. Several categories of materials are known as efficient adsorbents for removal of different air pollutants, in which activated carbon, silica gel, alumina oxide, and several types of zeolites are the most common ones [16]. While activated carbon is widely used, however, it has several disadvantages including: inflammability risk, low thermal stability, pores blockage, and problems associated with regeneration processes [2; 11; 12; 17]. Activated carbon is not a selective adsorbent, and we cannot control and tune its pore size because of its amorphous structure [18]. In order to overcome the problems associated with the commercially-available adsorbents (e.g., activated carbon), development of new porous materials as more efficient adsorbents is an emerging area of research with massive interest. Metal organic frameworks (MOFs) or organic-inorganic hybrid solids, also known as porous coordination polymers (PCPs), have attracted great attention in recent years because of their unique structural chemistry including, but not limited to, high surface area, their possibility to incorporate functional groups, and tunable porosities [19; 20]. MOFs can be used as adsorbents [21; 22], and in catalysis [23; 24; 25], drug delivery [26], chemical sensors [27], and for different energy applications [28]. Zeolitic imidazole frameworks (ZIFs) are a subgroup of MOFs with a crystal structure similar to zeolites. In ZIF structure, a metal ion (M = Zn\({}^{2+}\) or Co\({}^{2+}\)) replaces Si and Al tetrahedral and an imidazolate (Im) linker replaces the bridging oxygen in zeolites. The composed M-Im-M angle is \(\sim\)145\({}^{\circ}\), which is similar to the Si-O-Si angle of zeolite crystal structure [29; 30; 31; 32].