## 1 Introduction  
Treatment of oily wastewater has attracted growing attention from the academic and industrial sectors in recent years due to the growing global environmental hazards associated with the discharge of industrial and domestic sewage as well as oil spills [1, 2]. Traditional disposal techniques used to treat oily wastewater, such as gravity-driven separation, oil skimmers, in situ burning, methods that rely on centrifugal separation, dispersion with chemical reagents and microbial treatments, have low efficiencies, high costs and can even cause secondary pollution to the environment [3, 4, 5]. Moreover, treatment of oily wastewater composed of surfactant-stabilized emulsions is even more challenging [6, 7, 8, 9, 10]. Therefore, novel techniques and materials that efficiently separate immiscible and emulsified oil/water mixtures are needed for practical use in wastewater treatment. The high porosity, interconnected pore structure and unique wettability of porous materials make them highly valued in oily wastewater treatment [11; 12]. Moreover, the surface wettability of porous materials can be adjusted to tune their selectivity and separation ability for oil/water mixtures [13; 14; 15; 16; 17; 18; 19; 20]. For example, [PERSON] et al. [21] modified Fe\({}_{3}\)O\({}_{4}\) nanoparticles with siloxanes and then used the modified nanoparticles to adjust the hydrophobicity of polyurethane foams by a simple drop-coating method. The resulting magnetic materials were able to remotely magnetically absorb oil from water and achieve gravity-driven oil/water separation. [PERSON] et al. [22] prepared a superhydrophobic/superoleophilic material based on the surface modification of wood fibers that showed excellent performance in oil/water separations. Moreover, the prepared material could be used in multiple environments and achieved highly efficient absorption- and filtration-based separation of oil/water mixtures. While these materials were able to absorb oil from wastewater, treating large-scale oil spills with such types of oil sorbents is a time-consuming and labor-intensive task. A large amount of absorbent material is often required because the absorbents have a limited capacity for the oils [23]. Moreover, absorbent-based separations are not scalable for large-scale oily wastewater treatment because the oil/water mixtures must be collected before it can be filtered [24; 25; 26; 27]. Therefore, in order to simplify the separation process, it is necessary to design and manufacture devices based on oil absorbing materials that can continuously and efficiently handle oily wastewater. Towards this goal, [PERSON] et al. developed an in situ oil collection device that was aided by the application of external force [28]. Such continuous oil collection processes require oil absorbing materials with high mechanical performances as well as excellent hydrophobic and lipophilic properties [29]. Many strategies have been developed for the modification of commercial melamine foams, polyurethane foams or metal foams (pore sizes ranging from 100 to 500 \(\upmu\)m) to create materials with the desired characteristics for the continuous clean-up of large-scale oil spills [22; 30; 31; 32]. Although the design of these superwetting foams is exquisite, the pore structure of the matrix material is not sufficient to act as particle sieves and separate emulsions, especially emulsions with particle sizes less than 20 \(\upmu\)m [33; 34; 35]. On the other hand, the surface modification of the matrix material requires either complicated procedures or expensive equipment, and even fluorochemicals are utilized to reduce the surface energy, causing secondary environmental pollution. Therefore, the exploration of new strategies for the preparation of superwettable materials with controlled pore structures is needed to realize the continuous and efficient separation of immiscible and emulsified oil/water mixtures.