Mixed-Valence Bimetallic Ce/Zr MOF-Based Nanoarchitecture: A Visible-Light-Active Photocatalyst for Ciprofloxacin Degradation and Hydrogen Evolution

Abstract

A mixed-valency bimetallic Ce/Zr MOF with Ce 3+ / Ce 4+ ions incorporated and an oxygen vacancy-rich singlecomponent photocatalyst have been designed through the onestep solvothermal route to harness photons from the visible-light spectrum for green energy (H 2 ) generation and ciprofloxacin (CIP) degradation. The one-pot-engineered bimetallic Ce/Zr MOF shows visible-light-active characteristics accompanied by a narrower band gap, along with enhanced exciton separation and superior ligand-to-metal charge transfer (LMCT), due to the presence of an interconvertible Ce 3+ /Ce 4+ ions pair in comparison to its pristine MOF counterpart. The Ce ion insertion led to increase in electron density around the Zr 4+ ion, along with generation of some oxygen vacancies (OV), which cumulatively led to the rise in the photo-reaction output. The synthesized UNH (Ce/Zr 1:1) MOF displayed a boosted photocatalytic H 2 production rate of 468.30 μmol h −1 (ACE = 3.51%), which is around fourfolds higher than that of pristine MOFs. Moreover, for CIP photodegradation, the UNH (Ce/Zr 1:1) shows an enhanced efficiency of 90.8% and follows pseudo-first-order kinetics with a rate constant of 0.0363. Typically, the active species involved in the photo-redox reaction of the CIP photodegradation follows the order hydroxyl radical (OH • ) < superoxide radical (O 2•− ), as confirmed by the TA and NBT tests. Consequently, the bimetallic Ce/Zr MOF can be readily employed as a robust photocatalyst with enhanced tendencies towards CIP degradation and H 2 evolution.

Three-Dimensional Hierarchical Seaweed-Derived Carbonaceous Network with Designed g-C3N4 Nanosheets: Preparation and Mechanism Insight for 4-Nitrophenol Photoreduction

“…Owing to the rapid demand for energy and the concerning issue of environmental pollution, semiconductor photocatalysts have aroused widespread attention. − Among them, photocatalysts such as ZrO 2 , TiO 2 , SiC, and SnO 2 have attracted tremendous interest due to their low cost, environmental friendliness, nontoxicity, high stability, and excellent photocatalytic activity. − However, the limited photocatalytic activity under visible light and the complicated fabrication process restrict their large-scale applications. Therefore, many scientific researchers have concentrated on the development of efficient photocatalysts, which can directly decompose water or degrade environmental pollutants using solar energy. − In the past few years, g-C 3 N 4 has gained much attention as a typical metal-free semiconductor photocatalyst because of its widespread applications, such as removal of toxic heavy metal ions, degradation of dye pollutants, selective organic transformation to fine chemicals, and photocatalysis for hydrolytic hydrogen production. − …”

Metal organic framework-based Janus nanomaterials: rational design, strategic fabrication and emerging applications

“…Thus, they can be used to overcome the problems faced by traditional nanomaterials having low active surface area and functionalities. [5][6][7][8][9][10][11][12][13][14] By this way, MOFs and their derived products can be potentially suited for a myriad of applications, involving biomedicines, catalysis, electro-catalysis, pollutant removal, energy storage, molecular propulsion, and others. [15][16][17] Apart from that, researchers have lately begun combining MOFs with other functional materials in order to impart additional functions to these nanoparticles and hence, paving the way for an advanced class of nanomaterials.…”

Titanium–Porphyrin Metal–Organic Frameworks as Visible-Light-Driven Catalysts for Highly Efficient Sonophotocatalytic Reduction of Cr(VI)

“…Metal–organic frameworks (MOFs), integrated with metal clusters/ions and organic linkers through coordination bonds, are well known as a kind of functional hybrid materials. − Through appropriately selecting these inorganic or organic building blocks, the photophysical process of MOFs could be effectively regulated and controlled at the molecular level, which promoted the preparation and application of MOF photocatalysts. − Compared with some 1D or 2D semiconductor photocatalysts, MOFs possess the superiority of easily functionalized pore structures, high density of catalytic sites, and large specific surface area, which is convenient for adsorption and conversion of Cr­(VI) . In recent years, numerous MOFs were designed through combining photoactive ligands (e.g., organometallic complexes and porphyrin derivatives) and high valence metallic ions (e.g., Zr 4+ , Fe 3+ , and Ti 4+ ), where this kind of MOF possesses visible-light harvesting, robust nature, and various types of catalytic active sites, exhibiting notable performance in the photocatalytic Cr­(VI) reduction system. − Although the open frameworks endow MOFs with a large specific surface area, the long range-ordered pore structure also hampers the photogenerated charge transfer in the structures, limits the substrate or product mass transfer in the channel of MOFs, and ultimately affects the catalytic efficiency of reactions. , Hence, a new MOF-based photocatalytic Cr­(VI) reduction system should be developed to improve the abovementioned issues.…”