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

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