Microporous Na-Nd Heterometallic Organic Frameworks for C₂H₂/CO₂ and C₃H₄/C₃H₆ Separation

Selective adsorption of alkynes using porous materials is an energy- and cost-saving potential separation technique compared to low-temperature distillation. However, developing suitable adsorbents remains a significant challenge due to the high similarity between alkynes and impurities. Herein, we utilize a lanthanide-metalloligand strategy to design a Na-Nd heterometallic organic framework (NXU-1-Nd; NXU, Ningxia University) for the effective separation of alkynes from C₂H₂/CO₂ and C₃H₄/C₃H₆ mixtures. The material features a "pillared-layer" structure with the chemical formula {[Nd₃(ODA)₃(PDDB)₃Na₂]·1.8H₂O}_n (H₂ODA = oxydiacetic acid, H₂PDDB = 4,4'-(pyridazine-3,6-diyl)-dibenzoic acid), possessing open microporous channels and abundant Lewis basic sites. Through static adsorption isotherm measurements, NXU-1-Nd exhibits high adsorption capacities of 103.7 cm³ g^-1 for C₂H₂ and 120.2 cm³ g^-1 for C₃H₄, along with a low adsorption enthalpy. Dynamic breakthrough experiments revealed that NXU-1-Nd can effectively separate C₂H₂/CO₂ and C₃H₄/C₃H₆ mixtures while demonstrating excellent reusability and stability.