Highly active and selective propylene dimerization enabled by MOF-supported diimine-ni catalys

Propylene is a key monomer for producing polypropylene and ethylene-propylene rubbers. With the rapid expansion of propylene production capacity in recent years, converting propylene into higher-value oligomers using transition-metal catalysts has become an increasingly attractive yet challenging direction. Among these processes, propylene dimerization produces a mixture of C6 olefin isomers, which serve as critical building blocks for polymers and other chemicals.

A research team led by Li Mingyuan, Wang Le, and Cai Zhengguo from the State Key Laboratory of Advanced Fiber Materials, College of Materials Science and Engineering at Donghua University, has developed a heterogeneous diimine-nickel catalyst through sequential ligand insertion into PCN-700, a robust Zr-based MOF, followed by chelation of Ni centers. This site-specific assembly affords a robust active center for propylene dimerization with superior activity.

The catalyst, denoted as diimine-Ni@PCN-701, achieves a remarkable TOF of 56900 h⁻¹ under optimized conditions (400 kPa propylene pressure, Al/Ni molar ratio of 400, using EtAlCl₂ as cocatalyst), significantly outperforming its homogeneous analogue (19900 h⁻¹). The study demonstrates that the electron-withdrawing ability of the Zr₆O₄(OH)₄ clusters reduces the electron density at the Ni center, accelerating the rate of propylene coordination insertion. Meanwhile, the MOF pores provide steric confinement that steers the reaction pathway toward two consecutive 2,1-insertions, yielding 4M2P as the major product, which accounts for up to 57.6% of the total product.

The catalyst exhibits 100% selectivity for propylene dimerization, with no detectable trimers or higher oligomers. Product distribution is influenced by propylene pressure and Al/Ni molar ratio, with the optimal conditions yielding the highest activity. Importantly, no metal leaching (Zr or Ni) is detected after the reaction, confirming the heterogeneous nature and excellent stability of the catalyst.

This work not only highlights the potential of MOFs as platforms for heterogeneous catalysis but also establishes a general strategy for designing highly active and shape-selective olefin oligomerization catalysts through the precise construction of active sites. The work entitled “MOF-Supported Diimine-Ni Catalyzed Highly Active Propylene Dimerization” was published in Journal of Donghua University (English Edition) (published in Issue 02, 2026).