Synthesis of Ni2+ cation modified TS-1 molecular sieve nanosheets as effective photocatalysts for alcohol oxidation and pollutant degradation

Abstract

Improvement of the charge separation of titanosilicate molecular sieves is critical to their use as photocatalysts for oxidative organic transformations. In this work, MFI TS-1 molecular sieve nanosheets (TS-1 NS) were synthesized by a low-temperature hydrothermal method using a tailored diquaternary ammonium surfactant as the structure-directing agent. Introducing Ni2+ cations at the ion-exchange sites of the TS-1 NS framework significantly enhanced its photoactivity in aerobic alcohol oxidation. The optimized Ni cation-functionalized TS-1 NS (Ni/TS-1 NS) provide impressive photoactivity, with a benzyl alcohol (BA) conversion of 78.9% and benzyl aldehyde (BAD) selectivity of 98.8% using O2 as the only oxidant under full light irradiation; this BAD yield is approximately six times greater than that obtained for bulk TS-1, and is maintained for five runs. The excellent photoactivity of Ni/TS-1 NS is attributed to the significantly enlarged surface area of the two-dimensional morphology TS-1 NS, extra mesopores, and greatly improved charge separation. Compared with bulk TS-1, Ni/TS-1 NS has a much shorter charge transfer distance. The as-introduced Ni species could capture the photoelectrons to further improve the charge separation. This work opens the way to a class of highly selective, robust, and low-cost titanosilicate molecular sieve-based photocatalysts with industrial potential for selective oxidative transformations and pollutant degradation.