Basic Aluminum Benzoate is Low-Cost, Porous, and Superhydrophobic

Superhydrophobic materials are of tremendous application prospects, but they typically need to be prepared by relatively expensive reagents or complex treatments. Here, we report a simple aluminum-based coordination polymer [Al(OH)(ba)₂] (MCF-66, Hba = benzoic acid), which can be facilely synthesized by various low-cost raw materials. For example, based on the simple acid-base reaction between Hba and Al(OH)₃ (raw material costs ∼ 1 USD kg^-1), MCF-66 can be synthesized in ca. 100% yield without using any solvent or additive, with water as the sole byproduct. MCF-66 consists of insufficiently packed butterfly-like chains, with hydrophobic phenyl rings exposed on the crystal surfaces, enabling superhydrophobicity. The compressed pellet showed a high water contact angle of 152°, which identified MCF-66 as a rare superhydrophobic material. Although the small discrete pores formed between the chains are just slightly larger than H₂, it can deform to adsorb various small molecules and show special separation behavior for the n-C₄H₁₀/i-C₄H₁₀ mixture. MCF-66 can also be directly grown on aluminum meshes for highly efficient oil-water separation (8.8 × 10³ L m^-2 h^-1 bar^-1).