An MOF-Based Single-Molecule Propylene Nanotrap for Benchmark Propylene Capture from Ethylene

Highly selective capture and separation of propylene (C3H6) from ethylene (C2H4) presents one of the most crucial processes to obtain pure C2H4 in the petrochemical industry. The separation performance of current physisorbents is commonly limited by insufficient C3H6 binding affinity, resulting in poor low-pressure C3H6 uptakes or inadequate C3H6/C2H4 selectivities. Herein, we realize a unique single-molecule C3H6 nanotrap in an ultramicroporous MOF material (Co(pyz)[Pd(CN)4], ZJU-74a-Pd), exhibiting the benchmark C3H6 capture capacity at low-pressure regions. This MOF-based nanotrap features the sandwichlike strong multipoint binding sites and the perfect size match with C3H6 molecules, providing an ultrastrong C3H6 binding affinity with the maximal Qst value (55.8 kJ mol–1). This affords the nanotrap to exhibit one of the highest C3H6 uptakes at low pressures (60.5 and 103.8 cm3 cm–3 at 0.01 and 0.1 bar) and record-high C3H6/C2H4 selectivity (23.4). Theoretical calculations reveal that the perfectly size-matched pore cavities combined with sandwichlike multibinding sites enable this single-molecule C3H6 nanotrap to maximize the C3H6 binding affinity, mainly accounting for its record low-pressure C3H6 capture capacity and selectivity. Breakthrough experiments further confirm its excellent separation capacity for actual 1/99 and 50/50 C3H6/C2H4 mixtures, affording the remarkably high pure C2H4 productivities of 17.1 and 3.4 mol kg–1, respectively.