Construction of Pillared-Layer MOF as Efficient Visible-Light Photocatalysts for Aqueous Cr(VI) Reduction and Dye Degradation

Abstract

By using a controllable pillared-layer method, a novel visible-light responsive metal–organic framework (MOF) photocatalyst NNU-36 has been rationally constructed. The synthesized NNU-36 is of broad-range visible light absorption and good chemical stability which are beneficial to its application of photocatalysis. Photocatalytic experiments reveal that NNU-36 is highly efficient for Cr­(VI) reduction and dye degradation in aqueous solution under visible light irradiation. Control experiments show that the pH value is vital for Cr­(VI) reaction, and meanwhile, the use of hole scavenger of methanol promotes the photocatalytic reduction significantly. It has been also demonstrated that NNU-36 is efficient for dye degradation, in which the introduction of hydrogen peroxide (H2O2) significantly enhances the photocatalytic efficiency of dye degradation. This study illustrates that the introduction of hole scavengers or oxidants in the MOF-mediated photocatalytic reaction is a feasible approach to enhance the catalytic efficiency by suppressing the recombination of photoexcited electron–hole pairs in MOFs photocatalysts.

Highly Efficient Photocatalytic Degradation of Dyes by a Copper–Triazolate Metal–Organic Framework

“…As generally accepted, hydroxyl radicals (⋅OH) are the active species in the H 2 O 2 ‐involved photocatalytic reactions over MOFs . To verify the major active species in our system, tert ‐butyl alcohol (TBA) was used as a scavenger of hydroxyl radicals in the degradation reaction . As illustrated in Figure , the addition of TBA greatly depressed the photocatalytic efficiency for the degradation of RhB.…”

“…[34] Xing's group recently reported that NNU-36 is ah ighly efficient heterogeneous photocatalystf or the reduction of aqueous Cr VI and degradation of dyes (rhodamine B: RhB;r hodamine 6G:R 6G, MLB). [35] These research reports, together with others, [36][37][38][39] have revealed the enormous potential held by MOFs for their use in photocatalytic removal of environmental contaminants.…”

“…[71][72][73] To verify the major active speciesi n our system, tert-butyl alcohol (TBA) was used as as cavenger of hydroxyl radicals in the degradation reaction. [35,74,75] As illustrat- ed in Figure 9, the addition of TBA greatly depressed the photocatalytic efficiencyf or the degradation of RhB. In the presence of 100 mL( or 200 mL) of TBA,7 0.2 %( or 64.2 %) of RhB was degraded after 22 min, and the first-order reaction rate constantd ropped to only approximately 1/4 of the original value (0.190 min À1 vs. 0.056 (or 0.044)min À1 ).…”

“…found that the efficient degradation of methylene blue (MLB) can be achieved under irradiation of UV or visible light by using MIL‐53(Fe) as photocatalyst . Xing's group recently reported that NNU‐36 is a highly efficient heterogeneous photocatalyst for the reduction of aqueous Cr VI and degradation of dyes (rhodamine B: RhB; rhodamine 6G: R6G, MLB) . These research reports, together with others, have revealed the enormous potential held by MOFs for their use in photocatalytic removal of environmental contaminants.…”

Construction of visible‐light‐responsive metal–organic framework with pillared structure for dye degradation and Cr(VI) reduction

“…The pillared‐layer approach is one of the few controllable ways to synthesize MOFs with fixed structural features, which typically relies on the introduction of bipyridine pillaring ligand combined with other carboxylate ligands to construct mixed‐linker MOFs with pillared‐layer structures. Studies have demonstrated that this method is highly feasible for the preparation of a series of isostructural MOFs with excellent physical and chemical stability . More importantly, it provides an easy way to realize desirable functionality of MOFs through conventional ligand modification.…”