Constructing thiophene-decorated organic molecular sieves as efficient photocatalysts for removing chromium(vi)

Abstract

The utilization of photocatalysis for the reduction of highly toxic Cr(VI) to less toxic Cr(III) presents a cost-effective and sustainable green approach. It is crucial to design and produce efficient, stable, and recyclable photocatalysts for the photoreduction of Cr(VI). In this study, thiophene units were successfully incorporated into organic molecular sieves via a Suzuki–Miyaura coupling reaction, resulting in two thiophene-based OMSs (TP-OMS1 and TP-OMS2). The experiments showed that both TP-OMSs could efficiently convert Cr(VI) to Cr(III) under visible light without sacrificial agents or pH adjustment. Compared with TP-OMS2, TP-OMS1 exhibited higher reduction efficiency (TP-OMS1 > 99%, TP-OMS2 > 94% after 2 h). Even at a concentration of 100 mg L⁻¹ of Cr(VI), 5 mg of TP-OMS1 can still effectively catalyze the photoreduction within 4 h. TP-OMS1 exhibits exceptional stability and recyclability, and can be reused for at least 8 runs without significant loss in activity or structural integrity. Therefore, incorporating thiophene into TP-OMSs can enhance their photocatalytic performance for the Cr(VI) reduction, facilitating the removal of toxic pollutants. The mechanism of porous catalysis has also been thoroughly investigated here.