Elsevier

Catalysis Communications

Volume 134, 10 January 2020, 105859
Catalysis Communications

Short communication
Degradation of phenol using a peroxidase mimetic catalyst through conjugating deuterohemin-peptide onto metal-organic framework with enhanced catalytic activity

https://doi.org/10.1016/j.catcom.2019.105859Get rights and content

Highlights

  • Precipitation and cross-linking strategy for construction of peroxidase mimetic (DhHP-6-c-ZrMOF).

  • Characterization of the immobilization of DhHP-6 onto ZrMOF.

  • DhHP-6-c-ZrMOF delivered enhanced kinetics performance, peroxidase activity, pH stability.

  • Synergistic mechanism offers the material excellent phenol degradation capacity and recoverability.

Abstract

Deuterohemin-β-Ala-His-Thr-Val-Glu-Lys (DhHP-6), a novel Deuterohemin-containing peptide mimetic of natural microperoxidase-11 (MP-11), was successfully immobilized onto NH2-UIO-66 (ZrMOF) by precipitation and cross-linking strategy to obtain a peroxidase mimetic, DhHP-6-c-ZrMOF. The synergy between components offers DhHP-6-c-ZrMOF excellent kinetics performance, peroxidase activity, pH stability, and phenol degradation capacity. Up to 98.0% of phenol could be degraded in 120 min when utilizing DhHP-6-c-ZrMOF as heterogeneous Fenton catalyst. Notably, DhHP-6-c-ZrMOF delivered outstanding recoverability with an 80.2% degradation ratio of phenol after four recycles. The efficient peroxidase mimetic can potentially be used as a promising catalyst for the high-efficiency degradation of phenol pollutants.

Introduction

Among various water pollutants, phenol and its derivatives are widely present in wastewater from industrial processes, such as petrochemical manufacture, steel smelting, and pharmaceutical industries [1]. As representative advanced oxidation processes (AOPs), heterogeneous Fenton processes with separable solid catalysts have been widely reported to removal phenol in mild conditions and produce few residual sludges [2,3]. However, most of these catalysts are related to weak catalytic activity, low dispersion and stability. It is highly necessary to construct efficient and stable heterogeneous catalysts for the Fenton process.

Recently, well-studied enzymes such as horseradish peroxidase (HRP), laccase, and nanozyme have been successfully utilized in the Fenton/Fenton-like process to remove the phenolic contaminants [[4], [5], [6], [7]]. However, natural enzyme catalysts revealed some disadvantages in aqueous-system catalysis, such as low stability and recovery, high environmental sensitivity, as well as time-consuming preparation and purification [[8], [9], [10]]. Deuterohemin-β-Ala-His-Thr-Val-Glu-Lys (DhHP-6) is a novel peptide mimetic of nature microperoxidase-11 (MP-11), which consists of a deuterohemin prosthetic group bonded to six amino acid residues [11]. As a unique type of peroxidase mimetic, which is easy to synthesize, DhHP-6 possesses well-defined structure, high stability, and most of all, vigorous peroxidase activity [12,13]. Currently, DhHP-6 has been widely applied in biology and chemistry, such as biocatalysis, biotherapy, and atom transfer radical polymerization (ATRP) catalysis [[14], [15], [16]]. Structure and characteristics of DhHP-6 suggest that it might be an efficient catalyst for the Fenton process; however, no relevant work has been reported as far as we know. Besides, immobilization of enzymes to appropriate substrate materials have been proved to enhance the catalytic activity and prevent aggregation. Therefore, a suitable substrate material is necessary for DhHP-6 to work as a heterogeneous Fenton catalyst effectively and efficiently.

Metal-organic frameworks (MOFs) are associated with a series of desirable properties such as high surface areas, adjustable pore sizes, and surface modifiability. Therefore, they showed considerable influences in numerous fields such as catalysis [17], gas adsorption [18], separation [19], drug delivery, and energy storage [20,21]. Significant efforts have been made to develop enzyme guest species (HRP, GOx, MP-11) encapsulated MOFs and progressed a long way [[22], [23], [24], [25]]. However, the catalytic activity, efficiency, and stability of modified enzyme composites are impeded by their metal leaching and remote catalytic sites. Further development is significant to optimize the overall performance of this unique type of hybrid material.

Herein, Zr-MOF (NH2-UiO-66) was selected as the support for DhHP-6 not only because of its excellent properties similar to other MOFs, but also the superior chemical stability in acid-base and oxidative environment, and the possibility of post-synthetic modification (Lewis-basic amine groups). Specifically, the peroxidase mimetic catalyst (DhHP-6-c-ZrMOF) was successfully synthesized by employing a strategy of precipitation and cross-linking strategy. Systematic analyses were carried on the DhHP-6-c-ZrMOF. The as-synthesized heterogeneous Fenton catalyst with outstanding recoverability exhibited excellent kinetics performance, peroxidase activity, pH stability, and phenol degradation capacity.

Section snippets

Materials

DhHP-6 was kindly provided by Dr. Liping Wang from School of Life Sciences, Jilin University (Changchun, China). All other chemicals were of the highest grade purchased from Energy Chemical and used as received.

Synthesis of ZrMOF and DhHP-6-c-ZrMOF

The synthesis of ZrMOF was performed according to a previous report [26]. Typically, DhHP-6-c-ZrMOF was prepared as follows, 25 mg of ZrMOF was mixed with 6 mg of DhHP-6 in 2 mL PBS buffer (10 mM, pH = 7.4) under sonication for 10 min, followed by adding 8 mL of saturated ammonium

Result and discussion

The immobilization of DhHP-6 onto ZrMOF is illustrated in Scheme 1. Firstly, saturated ammonium sulfate was used to precipitate DhHP-6 onto ZrMOF. Subsequently, glutaraldehyde (GA), a universal protein cross-linking agent, was added to form stabilized covalent bonds between DhHP-6 and ZrMOF. As shown in Fig. S1, DhHP-6-c-ZrMOF presented a colour of reddish brown which distinctly different from the yellow ZrMOF. Effects of experimental parameters on enzyme utilization and phenol oxidative

Conclusions

In summary, peroxidase mimetic (DhHP-6-c-ZrMOF) was synthesized by precipitation and cross-linking strategy. The immobilization of DhHP-6 onto the surface of ZrMOF was achieved through stable covalent bonds. The kinetics performance, peroxidase activity, and pH stability of DhHP-6-c-ZrMOF were systematic studied and exhibited remarkable improvements compared with free DhHP-6. Furthermore, the as-synthesized heterogeneous Fenton catalyst also delivered excellent phenol degradation capacity and

Acknowledgments

This work was supported by Science and Technology Development Project of Science and Technology Department of Jilin Province [NO. 20180201086G X].

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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