A sulfonic acid-functionalized covalent organic framework for efficient catalytic hydration of α-alkenes to secondary alcohols

Abstract

Secondary alcohols are high-value chemical intermediates extensively employed in solvents, cleaners, and disinfectants. Their synthesis via direct acid-catalyzed hydration of α-olefins is constrained by low conversion efficiency and rapid catalyst deactivation. To overcome these limitations, TAPB–DHTP–SO₃H, a sulfonic acid-functionalized covalent organic framework (COF) that integrates structural robustness, high crystallinity, and uniformly distributed Brønsted acid sites, was rationally designed and fabricated. With a BET surface area of 259.4 m² g⁻¹ and an average pore diameter of 2.3 nm, the porosity of the TAPB–DHTP–SO₃H COF facilitates rapid diffusion of α-olefin substrates such as 1-heptene, thereby ensuring full utilization of the acid sites. Under mild hydration conditions, the TAPB–DHTP–SO₃H COF, together with co-catalyst trifluoroacetic acid, promotes a tandem esterification–hydrolysis sequence, achieving over 89% conversion of 1-heptene with 96% selectivity to 2-heptanol. The catalyst retains its activity after six consecutive cycles and delivers consistent performance across a range of C5–C11 linear α-olefins and other internal olefins, demonstrating excellent operational stability and substrate generality. These findings establish a structure–function rationale for COF-based solid acids in olefin hydration and provide a reproducible and scalable platform for upgrading olefins to high-value alcohols.