BiOCl-Coated UiO-66-NH₂ Metal–Organic Framework Nanoparticles for Visible-Light Photocatalytic Cr(VI) Reduction

Abstract

Pollutants in wastewater, such as Cr(VI) is a continuous threat to our ecological system and human well-being because of its high noxiousness and latent carcinogenicity. Photocatalytic Cr(VI) reduction is the most suitable and eco-friendly way to convert the toxic Cr(VI) to environmentally friendly Cr(III). Porous metal−organic frameworks (MOFs) based nanocomposites are emerging green photocatalysts for Cr(VI) reduction due to their unique characteristics such as high photoconductivity, large surface area, and suitable porous structure. Herein, the preparation of ultrathin BiOCl sheets over UiO-66-NH 2 is reported for the first time at room temperature via a simplistic in situ synthetic process to yield a series of UiO-66-NH 2 @BiOCl-UTN's heterogeneous nano composites. The activity toward Cr(VI) reduction was tested under visible-light. UiO-66-NH 2 @BiOCl-UTN's heterogeneous nanocomposites exhibited better performance as equated to individual BiOCl and UiO-66-NH 2 , particularly the composite with Bi 3+ mole ratio of 5 mM surpassed other composites for photocatalytic Cr(VI) reduction. Furthermore, boosted visible-light absorption (λ > 420 nm) was observed in the presence of −NH 2 moiety on the organic linker. The excellent photocatalytic activity was attributed to the synergistic effect between BiOCl and UiO-66-NH 2 for the effective separation of photogenerated electron−hole suppressing their recombination. Through active species trapping experiments, electron spin resonance measurements, and electrochemical analysis, the reliable mechanism was predicted and confirmed. Moreover, heterogeneous nanomaterial retained its structure and activity for four consecutive cycles demonstrating its superior stability.

Heterogeneous ZnS–zinc carbonate hydroxide micro-belts for Cr(vi) reduction under simulated sunlight

“…The decrease in the catalytic performance at pH = 2 was noticed because the ZnS-ZCH micro-belt could be unstable at strongly acidic condition. 28 Additionally, the effect of reaction temperature on the reduction efficiency was studied and the data are presented in Fig. 6D.…”

Photoatalytic Degradation of Organic Pollutants in Water Under Visible Light by NH2‐MIL‐125(Ti‐Zr)@BiOClxI1‐x Composite Photocatalyst

“…Hussain et al successfully synthesized BiOCl@UiO-66-NH 2 composite and degraded Cr(VI) under visible light. [8] The results showed that the reaction rate constant K is 35.8 and 19.6 times higher than isolated UiO-66-NH 2 and BiOCl, respectively. The MIL-53@BiOCl composite photocatalyst was prepared by Sheng Chao et al [15] The degradation rates of Rhodamine B by MIL-53@BiOCl-6 in 30 min was 59.2 %, while BiOCl and MIL-53 were about 39.2 % and 24.1 %, respectively.…”

“…Because of its cheap, non-toxic and stable characteristics, it is widely used in the field of photocatalytic degradation. [8][9][10] However, the lack of optical response in visible light limits its development. The current research shows that the performance of photocatalyst can be improved by constructing heterojunction.…”

“…Bi atom is connected to O atom by covalent bond, and van der Waals force exists between Bi atom and Cl atom. Because of its cheap, non‐toxic and stable characteristics, it is widely used in the field of photocatalytic degradation [8–10] . However, the lack of optical response in visible light limits its development.…”

“…Hussain et al . successfully synthesized BiOCl@UiO‐66‐NH 2 composite and degraded Cr(VI) under visible light [8] . The results showed that the reaction rate constant K is 35.8 and 19.6 times higher than isolated UiO‐66‐NH 2 and BiOCl, respectively.…”