Construction of a Melamine Sponge with Balanced Amphiphilic Surfaces for Efficient Promotion of Methane Hydrate Formation

Foam-based bed exhibits significant efficiency in promoting the formation of methane hydrate (MH). However, the relationship between the hydrating performance and its surface wettability remains unclear. In this study, the surface wettability of melamine sponge (MS) was regulated using covalent organic frameworks (COFs), and quantitatively elucidated the effects of wettability on MH formation. The results indicate that when the surface contact angle (CA) was approximately 90°, the hydrophilic–hydrophobic balance was optimal, achieving an induction time of 5.16 min, a storage capacity of 173.30 V/V, and a conversion rate of 89.74%. Mechanism analysis revealed that this balanced surface property not only promoted the adsorption and aggregation of water molecules and methane molecules and accelerated the formation and stability of hydrogen bond networks, but also achieved uniform distribution due to its moderate affinity, thereby maximizing the gas–liquid contact area. Its promoting effect is significantly superior to that of hydrophilic or hydrophobic surfaces. Moreover, the fixed bed with this balanced surface exhibited a multistage characteristic of “cold center, hot edge” during the dissociation process, completely dissociating within 100 min without any foam formation. Based on this, we further coupled with the efficient surfactant SCS, achieving transient initiation without an induction stage and increasing the storage capacity and conversion rate to 178.48 V/V and 93.80%, respectively. This study confirmed that the balance of hydrophilic–hydrophobicity is the key to the efficient formation of MH on the surface and provided important guidance for the design of MH reactors.