Highly recyclable Ti0.97Ni0.03O1.97 catalyst coated on cordierite monolith for efficient transformation of arylboronic acids to phenols and reduction of 4-nitrophenol

Abstract

A stable Ni²⁺ substituted TiO₂ catalyst (Ti_0.97Ni_0.03O_1.97) has been synthesized by a solution combustion method with an average crystallite size of 7.5 nm. Ti_1−xNi_xO_2−x (x = 0.01–0.06) crystallizes in the TiO₂ anatase structure with Ni²⁺ substituted in Ti⁴⁺ ion sites and Ni taking a nearly square planar geometry. This catalyst is found to be highly active in the transformation of diverse arylboronic acids to the corresponding phenols. The catalyst coated cordierite monolith can even be recycled for up to 20 cycles with a cumulative TOF of 1.8 × 10⁵ h⁻¹. In scale-up reactions, various phenols are synthesized by employing a single cordierite monolith. It also shows high performance in the reduction of 4-nitrophenol.