Multiple catalytic sites in MOF-based hybrid catalysts for organic reactions

Facile Recycling Strategy of Dyed Polyester Waste by Template-Based Synthesis of UiO-66 for Value-Added Transformation into Self-detoxifying Fabrics

Polyethylene terephthalate (PET) accounts for a significant portion of textile waste, and recycling strategies for this material have attracted much attention. This study proposes a facile and innovative PET recycling method applicable to environmental remediation that involves the conversion of dyed PET fabric waste into a value-added fabric. Herein, a template-based synthesis approach capable of growing a UiO-66 metal-organic framework (MOF) directly on a dyed PET fabric is reported. The advantage of this process lies in its simplicity, where the partial hydrolysis of PET followed by a zirconium chloride treatment results in the successful growth of UiO-66 on a dyed PET fabric with the concurrent removal of the dye without additional steps. The catalytic performance of the UiO-66-grown fabric was evaluated through the degradation of dimethyl 4-nitrophenyl phosphate (DMNP), a nerve agent simulant. The fabric produced by the simple metal treatment (Zr@PEThyd) exhibited excellent DMNP degradation performance with t1/2 = 43.3 min and maintained functional stability after a harsh washing procedure, an outcome attributed to the surface-assisted UiO-66 growth that ensured good bonding stability. The developed process is innovative in that it uses dyed PET waste as a template for the direct growth of UiO-66, simplifying the process without compromising the catalytic functionality. This research provides an informative option for a sustainable textile recycling strategy by transforming dyed PET waste into an advanced self-detoxifying material.

CoNi alloy anchored onto N-doped porous carbon for the removal of sulfamethoxazole: Catalyst, mechanism, toxicity analysis, and application

Developing highly efficient, stable, recyclable, and application value heterogeneous catalysts in advanced oxidation processes has essential application value in the degradation of refractory pollutants. In this paper, the CoNi alloy anchored onto N-doped porous carbon (CoNi-600@NC) catalyst was prepared using bimetallic doped metal-organic frameworks as precursors. The magnetic CoNi-600@NC can activate peroxymonosulfate (PMS) to degrade sulfamethoxazole (SMX). Therefore, SMX can be removed 100% within 25 min. CoNi-600@NC/PMS has a broad pH (3-9) application range, good applicability, and repeatability. Radical quenching, quantitative and electrochemical experiments proved that the degradation of SMX was dominated by free radical (Superoxide anions) and non-free radical pathways (surface-bound radicals). Mechanistic analysis showed that the interaction between Co-N_x/pyridine N-sites and graphitized carbon with PMS induced the formation of surface-bound active species. Moreover, CoNi nanoparticles promoted the redox cycle of metals. The synergistic catalytic mechanisms between the CoNi alloy and the abundant functional groups gave CoNi-600@NC excellent catalytic properties and applicability. Using density functional theory predicted the reaction sites of SMX and proposed four degradation pathways. The toxicity of intermediates was comprehensively evaluated. In addition, a CoNi-600@NC continuous flow reactor was constructed with a daily treatment capacity of 45 L and 100% SMX removal. This study expands the application of persulfate advanced oxidation technology by synthesizing recyclable magnetic catalysts and provides new synergistic degradation mechanisms for removing refractory organics.

Preparation of formate-free PMA@MOF-808 catalysts for deep oxidative desulfurization of model fuels

Due to the increasingly serious environmental problems caused by the combustion of sulfides in fuel, deep desulfurization of fuel became particularly urgent. Herein, the catalyst (PMA@MOF-808) of the Zr-based metal-organic framework (MOF-808) encapsulating phosphomolybdic acid (PMA) was prepared via a one-pot hydrothermal method. Besides, the formate ions of PMA@MOF-808 were removed by posttreatment with methanol, resulting in formate-free PMA@MOF-808-H catalysts with unsaturated open metal sites. The as-synthesized catalysts were systematically characterized by XRD, FT-IR, SEM, BET, TGA, ¹H NMR and XPS. The catalysts were also applied in catalytic oxidation desulfurization of fuel. The results indicated that the introduction of PMA and the removal of formate ions can improve the desulfurization performance of catalysts. Formate-free 0.2-PMA@MOF-808-H catalyst can reach 100% desulfurization rate for DBT. Besides, the kinetic properties were studied, and the apparent activation energy was 29.34 kJ/mol.

Supramolecular catalysis: the role of H-bonding interactions in substrate orientation and activation

Hydrogen bonding plays significant roles in various biological processes during substrate orientation and binding and therefore assists in assorted organic transformations. However, replicating the intricate selection of hydrogen bonds, as observed in nature, in synthetic complexes has met with only limited success. Despite this fact, recent times have seen the emergence of several notable examples where hydrogen bonds have been introduced in synthetic complexes. A few such examples have also illustrated the substantial role played by the hydrogen bonds in influencing and often controlling the catalytic outcome. This perspective presents selected examples illustrating the significance of hydrogen bonds offered by the coordination and the organometallic complexes that aid in providing the desired orientation to a substrate adjacent to a catalytic metal center and remarkably assisting in the catalysis.