Precision Cross-Section Sieving via a Deterministic-Lateral-Displacement-Inspired Metal-Organic Framework for...

The simultaneous separation of n/iso-C₄H₈ and n/iso-C₄H₁₀ mixtures presents a significant challenge due to the minimal difference in kinetic diameters (Δ < 0.2 Å) between n-butane and iso-butene. Inspired by the passive sorting mechanism of droplets via deterministic lateral displacement (DLD) in microfluidic architectures, we designed and synthesized a zinc-based metal-organic framework (CALF-20) featuring a canonical DLD array-like structure, wherein Zn' serves as periodic micropillar-like structural motifs. CALF-20 exhibits a critical pore cross-section precisely tailored to lie between the minimum cross-sectional areas of iso-C₄H₈ and n-C₄H₁₀, enabling simultaneous specific recognition of n-C₄H₈ and n-C₄H₁₀ while achieving complete steric exclusion of iso-C₄H₈ and iso-C₄H₁₀. The dual-ligand system in CALF-20 provides multiple cooperative binding sites for intelligent molecular recognition of linear C4 hydrocarbons, as further elucidated by theoretical calculations. Consequently, CALF-20 demonstrates high adsorption capacities of 2.7 and 2.5 mmol g^-1 for n-C₄H₈ and n-C₄H₁₀, respectively, while effectively excluding branched isomers. Dynamic breakthrough experiments validated the capability of CALF-20 to simultaneously produce high-purity (>99.999%) iso-C₄H₈ and n-C₄H₁₀ in a single operational step. Moreover, subsequent desorption yielded n-C₄H₈ and n-C₄H₁₀ with instantaneous purity exceeding 99.99%. This work establishes a DLD-inspired materials design paradigm, providing a groundbreaking and generalizable strategy for the efficient sieving separation of similarly challenging isomeric gas systems.