# Synergistic Cu–OH and zeolite confinement in Cu/MCM-22 for benzaldehyde-mediated Mukaiyama epoxidation of long-chain α-olefins

## TL;DR

A new catalyst, Cu/MCM-22, improves the selective epoxidation of long-chain olefins by combining copper sites with zeolite confinement.

## Contribution

The synergy of Cu–OH active sites and zeolite confinement in Cu/MCM-22 enhances selectivity and efficiency in epoxidation.

## Key findings

- Cu/MCM-22 achieves 97% conversion and 90% selectivity for 1-undecene epoxidation.
- Deactivating external Cu sites increases selectivity to 99% and aldehyde coupling efficiency by 3-fold.
- Zeolite confinement reduces energy barriers for benzaldehyde activation to 84 kJ·mol−1.

## Abstract

The Mukaiyama epoxidation of olefins, leveraging molecular oxygen and aldehydes to generate epoxides, is a cornerstone of sustainable synthesis but is hindered by compromising epoxide selectivity and aldehyde coupling efficiency due to the high reactivity of acylperoxy radicals. Here, we report a Cu/MCM-22 catalyst that synergistically integrates Cu–OH active sites with zeolite confinement to achieve exceptional selectivity and efficiency in the aerobic epoxidation of long-chain linear α-olefins. Comprehensive characterization, including transmission electron microscopy, X-ray absorption spectroscopy and Fourier-transform infrared spectroscopy, confirms atomically dispersed Cu2+ ions within MCM-22’s framework, enabling benzaldehyde activation via Cu2+/Cu+ redox cycling and H2O formation. Electron paramagnetic resonance and density functional theory (DFT) studies reveal that the confined pores of MCM-22 stabilize acylperoxy radicals, suppressing undesired pathways and promoting epoxide formation. Catalytic evaluations demonstrate 97% conversion and 90% selectivity for 1-undecene epoxidation, which was further improved to 99% selectivity by deactivating the Cu sites on the zeolite external surface, resulting in a roughly 3-fold increase in aldehyde coupling efficiency and significantly outperforming unconfined Cu/Al2O3 and Cu/SiO2. Kinetic analyses and DFT calculations highlight reduced energy barriers (84 kJ·mol−1) for benzaldehyde activation and enhanced chemoselectivity driven by zeolite confinement. This work elucidates the pivotal role of tailored active sites and spatial constraints in radical catalysis for selective epoxide synthesis.

An innovative strategy for Mukaiyama epoxidation is developed via a Cu/MCM-22 catalyst integrating atomically isolated Cu2+ ions with zeolite confinement, unraveling how Cu2+/Cu+ redox cycling enables benzaldehyde activation.