Hollow, mesoporous, eutectic Zn1-xMgxO nano-spheres as solid acid-base catalysts for the highly regio-selective O-methylation of 1, 2-diphenols

The highly regio-selective O-methylation of catechol with dimethyl carbonate (DMC), catalyzed by solid acid-base catalyst, is an environmentally friendly chemical process for industrial production of guaiacol. However, guaiacol yield below 84% and high reaction temperature above 280 °C limit its industrial application. Here, the hollow, mesoporous Zn1-xMgxO nano-spheres with a eutectic structure, denoted as Zn1-xMgxO HMNSs (x = 0.012-0.089), are facilely fabricated via the calcination of Mg2+/Zn2+ ions-adsorbed carbon spheres at 500 °C in air. In the O-methylation of catechol with DMC at 180 °C, Zn1-xMgxO HMNSs (x = 0.052) affords guaiachol in 95.5 % yield with a complete catechol conversion. Furthermore, the 89.0-95.3% mono-ether yields with high 1, 2-diphenol conversions (94.5-100%) are also obtained for the other 1, 2-diphenols bearing –CH3 and –Br groups. Moreover, a plausible mechanism for highly selective O-methylation of catechol with DMC is proposed, in which the single-site activation and double-sites activation of phenolic hydroxyls by the basic oxygen of Mg-O afford guaiacol and veratrole, respectively.