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Basic Aluminum Benzoate is Low-Cost, Porous, and Superhydrophobic
Summary:
The authors from Sun Yat-sen University and Guangdong Laboratory developed a one-dimensional aluminum–benzoate coordination polymer MCF-66 with intrinsic super-hydrophobicity (water contact angle 152°) and guest-induced framework flexibility, achieving quantitative solvent-free synthesis (~1 USD kg⁻¹) and high-flux oil–water emulsion separation (8.8×10³ L m⁻² h⁻¹ bar⁻¹).
Background:
1. Conventional super-hydrophobic materials rely on costly fluoropolymers or multi-step surface modification; few porous coordination polymers (PCPs) intrinsically exhibit water-repellency owing to a lack of low-cost, scalable, and crystal-engineering-friendly routes.
2. This work proposes an acid–base reaction between Al(OH)₃ and benzoic acid without solvent/additive, giving gram-scale, single-crystal-quality MCF-66; the hydrophobic phenyl-enriched surface and deformable ultra-micropores are disclosed for the first time in an Al-PCP system.
Research Content:
1. Synthesis
Solvent-free solid-state heating of Al(OH)₃ : Hba = 1 : 2.4 at 160 °C for 48 h, quantitative yield (~100 %); excess ligand recovered by sublimation (93 %).
Single crystals grown solvothermally with chelidonic acid modulator (38 % yield).
2. Characterizations
1) BET: N₂ uptake 3.36 mmol g⁻¹ at 77 K, pore volume 0.12 cm³ g⁻¹; ultra-micropores 2.2–2.7 Å, expanding 8.2 % under N₂.
2) SEM: rod-like crystallites 1–5 µm, exposing (001)/(010) hydrophobic facets.
3) Contact angle 152°, sliding angle < 3°; TG shows stability up to 300 °C and in pH 1–13 or boiling water for 7 d.
3. Application
n-C₄H₁₀/i-C₄H₁₀ breakthrough selectivity 11; n-C₄H₁₀ capacity 0.65 mmol g⁻¹ under mixture.
In-situ grown MCF-66/Al mesh (45 wt %) separates water-in-toluene emulsion, reducing water from 1 % to 0.04 % over 10 cycles without flux decay.
4. Mechanism
Guest-induced elastic expansion (ΔE_transf = 16.9 kJ mol⁻¹) opens 1-D channels; GCMC confirms N₂ binding −38.0 kJ mol⁻¹ in expanded phase.
π-π stacked butterfly chains shield hydrophilic Al–OH sites, rendering (001)/(010) surfaces water-repellent (MD water density ≈ 0 g cm⁻³).
Outlook:
MCF-66 demonstrates the feasibility of ultra-low-cost, intrinsically super-hydrophobic Al-PCPs synthesized under green conditions and directly integrated onto Al substrates for scalable oil-spill remediation and hydrocarbon separation.
Basic Aluminum Benzoate is Low-Cost, Porous, and Superhydrophobic
Authors: Zhi-Shuo Wang, Mu-Yang Zhou, Ding-Yi Hu, Xiao-Xian Chen, Jun-Xian Chen, Xue-Wen Zhang, Dong-Dong Zhou, Jie-Peng Zhang, Xiao-Ming Chen
DOI: 10.1021/jacs.5c12200
Link: https://doi.org/10.1021/jacs.5c12200
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