ZIF-71-programmed hydrophobic capillary gating in polylactic acid (PLA) composite aerogels for recyclable oil-water separation

PLA-based composite aerogels with high oil selectivity, good reusability, and gravity-driven transport capability are promising materials for oily-water treatment and spill remediation. However, many high-performance oil/water separation aerogels still rely on non-degradable matrices or fluorinated surface modifiers. Herein, ZIF-71 nanoparticles were incorporated into a polylactic acid (PLA) aerogel to construct a hydrophobic capillary-gating network through solution blending, water-assisted thermally induced phase separation, liquid-nitrogen freezing, and freeze-drying. The chlorinated imidazolate framework contributed hydrophobic/oleophilic domains, polyhedral roughness, and textural porosity, while the PLA matrix provided a lightweight biodegradable skeleton. Compared with pristine PLA, the optimized PZ71–3 aerogel increased the water contact angle from 114° to 136°, tensile strength from 0.088 to 0.166 MPa, elongation at break from 10% to 25%, and total pore volume from 0.0066 to 0.0091 cm³ g⁻¹ , while showing a BJH average pore diameter of 10.8 nm. The aerogel resisted a water head of 14.5 cm, selectively captured both floating heptane and sinking CCl₄, achieved oil recovery efficiencies of 98.2–99.2% with gravity-driven oil fluxes of 5300–17,200 L m⁻² h⁻¹ , and retained stable oil sorption capacity and flux over 20 cycles. Comparative benchmarking shows that PZ71–3 offers a balanced performance profile among MOF/polymer and biodegradable-polymer aerogels. This work demonstrates ZIF-71-induced hydrophobic capillary gating as an effective fluorine-free strategy for recyclable PLA-based sorbents for oil/water separation.