Introducing anthracene and amino groups into Ln-OFs for the photoreduction of Cr(vi) without additional photosensitizers or cocatalysts

Abstract

The utilization of catalysts with high stability and activity for the photoreduction of Cr(VI) is desirable but has many challenges. Since metal–organic frameworks (MOFs) have unique versatilities and facile structural modulations, we fabricated a stable MOF as a highly efficient photocatalyst by incorporating chromophores into lanthanide MOFs for efficient Cr(VI) reduction. Subsequently, a novel two-dimensional (2D) layered structural Sm(III) MOF (namely LCUH-100, [Sm₄(AAPA)₆(DMA)₂(H₂O)₄][DMA]₃[H₂O]₈, AAPA²⁻ = 5-[(anthracen-9-yl-methyl)-amino]-1,3-isophthalate, DMA = N,N′-dimethylacetamide) with sql topology symbol was constructed by incorporating dinuclear clusters, {Sm₂(COO)₆} and AAPA²⁻, which demonstrated excellent chemical and thermal stability, especially retaining its complete framework in aqueous solutions at a pH range of 2–12 for 24 h. Interestingly, LCUH-100 could efficiently and rapidly photocatalyze the reduction of Cr(VI) to Cr(III) without additional photosensitizers or cocatalysts. In the photoreduction of Cr(VI), LCUH-100 showed a high rate constant (k) of 0.186 min⁻¹ and a high Cr(VI) reduction rate of 1.67 mg_Cr(VI) g⁻¹_cata min⁻¹ at pH 2. Furthermore, the photocatalyst LCUH-100 could be reused for 5 cycles without any significant loss of catalytic activity. This work provides a new strategy for the exploitation of stable and efficient catalysts for the photocatalytic reduction of Cr(VI).