Finely dispersed AgPd bimetallic nanoparticles on a polydopamine modified metal organic framework for diverse catalytic applications

Asymmetric magnetic nanosnowman loaded with AgPd nanocage toward NIR-enhanced catalytic activity

Although bimetallic noble nanostructures often possess high activity in nanocatalysis, their controllable fabrication, tunable catalytic activity, and easy separation remain significant challenges. In this study, an Fe3O4@AgPd/Polydopamine (Fe3O4@AgPd/PDA) nanosnowman loaded with an AgPd nanocage was designed by a one-step template-disposition-redox polymerization method. The AgPd nanocage endowed the product with high catalytic activity for the reduction of organic pollutants (4-NP, MO, MB). Interestingly, under near-infrared (NIR) light, the catalytic kinetics of the Fe3O4@AgPd/PDA nanosnowman on catalytic reduction of organic pollutants increased by 2.6, 1.57, and 5.45 times, respectively. The asymmetric nanostructure facilitated the separation of electron-hole pairs, promoted electron transfer, and accelerated the catalytic activity. Density functional theory (DFT) analysis indicated that the electron transfer between the AgPd alloy and the Fe3O4 nanosphere played a critical role on the high catalytic activity. Moreover, Fe3O4@AgPd/PDA also demonstrated excellent catalytic activity in the Heck carbon-carbon coupling reaction with a >95% conversion rate and >99% selectivity. Owing to the well-encapsulated PDA shell and outstanding magnetic properties, the Fe3O4@AgPd/PDA nanosnowman exhibited good cyclic catalytic activity. With its multi-mode catalysis, NIR-enhanced catalytic activity, and easy separation, the Fe3O4@AgPd/PDA nanosnowman exhibits great application potential in nanocatalysis.

Imaging of intracellular protein aggregates through plasmon-assisted clusteroluminescence

The formation of clusters in non-aromatic molecules can give rise to unconventional luminescence or clusteroluminescence. Typically containing heteroatoms without extended conjugation or aromatic rings, these molecules have drawn much attention owing to the prospects of label-free biological imaging. However, their applications have been limited due to the lack of knowledge of the underlying mechanism. Herein, we have elucidated the mechanism of clusteroluminescence from proteins, which were explicitly aggregated using plasmonic silver nanoparticles. The nanoparticles promoted protein aggregation and induced nitrile formation on the surface, which, along with other lone-pair-containing heteroatoms, contributed to enhanced emission in the visible range. Remarkably, this makes imaging of proteins possible with visible excitations, as co-factor-lacking proteins generally undergo electronic transitions only in the ultraviolet range. Furthermore, the inherent protein-aggregating behaviour of plasmonic nanoparticles was harnessed for imaging of intracellular Huntingtin protein aggregates overexpressed in HeLa cells through clusteroluminescence. Significant plasmon-enhanced and red-shifted fluorescence emission was observed, which helped in the imaging and localization of the intracellular aggregates. Density functional theory calculations and transient absorbance spectroscopy were used to probe the molecular interactions at the protein-nanoparticle interface and the charge transfer states, further elucidating the role of nanoparticles and the emission mechanism. This technique thus opens alternate avenues for label-free fluorescence bioimaging.

Metalation of metal-organic frameworks: fundamentals and applications

Metalation of metal-organic frameworks (MOFs) has been developed as a prominent strategy for materials functionalization for pore chemistry modulation and property optimization. By introducing exotic metal ions/complexes/nanoparticles onto/into the parent framework, many metallized MOFs have exhibited significantly improved performance in a wide range of applications. In this review, we focus on the research progress in the metalation of metal-organic frameworks during the last five years, spanning the design principles, synthetic strategies, and potential applications. Based on the crystal engineering principles, a minor change in the MOF composition through metalation would lead to leveraged variation of properties. This review starts from the general strategies established for the incorporation of metal species within MOFs, followed by the design principles to graft the desired functionality while maintaining the porosity of frameworks. Facile metalation has contributed a great number of bespoke materials with excellent performance, and we summarize their applications in gas adsorption and separation, heterogeneous catalysis, detection and sensing, and energy storage and conversion. The underlying mechanisms are also investigated by state-of-the-art techniques and analyzed for gaining insight into the structure-property relationships, which would in turn facilitate the further development of design principles. Finally, the current challenges and opportunities in MOF metalation have been discussed, and the promising future directions for customizing the next-generation advanced materials have been outlined as well.

Two-Dimensional Lanthanide Metal-Organic Frameworks as a Platform for Sensing Pollutant and Nitrophenols Reduction

The discharge of harmful and toxic pollutants in water is destroying the ecosystem balance and human being health at an alarming rate. Therefore, the detection and removal of water pollutants by using stable and efficient materials are significant but challenging. Herein, three novel lanthanide metal-organic frameworks (Ln-MOFs), [La(L)(DMF)2(H2O)2]·H2O (LCUH-104), [Nd(L)(DMF)2(H2O)2]·H2O (LCUH-105), and [Pr(L)(DMF)2(H2O)2]·H2O (LCUH-106) [H3L = 5-(4-(tetrazol-5-yl)phenyl)isophthalic acid (H3TZI)] were solvothermally constructed and structurally characterized. In the three Ln-MOFs, dinuclear metallic clusters {Ln2} were connected by deprotonated tetrazol-containing dicarboxylate TZI3- to obtain a 2D layered framework with a point symbol of {42·84}·{46}. Their excellent chemical and thermal stabilities were beneficial to carry out fluorescence sensing and achieve the catalytic nitrophenols (NPs) reduction. Especially, the incorporation of the nitrogen-rich tetrazole ring into their 2D layered frameworks enables the fabrication of Pd nanocatalysts (Pd NPs@LCUH-104/105/106) and have dramatically enhanced catalytic activity by using the unique metal-support interactions between three Ln-MOFs and the encapsulating palladium nanoparticles (Pd NPs). Specifically, the reduction of NPs (2-NP, 3-NP, and 4-NP) in aqueous solution by Pd NPs@LCUH-104 exhibits exceptional conversion efficiency, remarkable rate constants (k), and outstanding cycling stability. The catalytic rate of Pd NPs@LCUH-104 for 4-NP is nearly 8.5 times more than that of Pd/C (wt 5%) and its turnover frequency value is 0.051 s-1, which indicate its excellent catalytic activity. Meanwhile, LCUH-105, as a multifunctional fluorescence sensor, exhibited excellent fluorescence detection of norfloxacin (NFX) (turn on) and Cr2O72- (turn off) with high selectivity and sensitivity at a low concentration, and the corresponding fluorescence enhancement/quenching mechanism has also been systematically investigated through various detection means and theoretical calculations.

CuCo Nanoparticle, Pd(II), and l-Proline Trifunctionalized UiO-67 Catalyst for Three-Step Sequential Asymmetric Reactions

Metal-organic frameworks (MOFs) have become a promising support for different active sites to construct multifunctional and heterogeneous catalysts. However, the related investigation mainly focuses on introducing one or two active sites into MOFs and trifunctional catalysts have been very rarely reported. Herein, non-noble CuCo alloy nanoparticles, Pd²⁺, and l-proline, as encapsulated active species, functional organic linkers, and active metal nodes, respectively, were successfully decorated to UiO-67 to construct a chiral trifunctional catalyst by the one-step method, which was further applied to asymmetric three-step sequential oxidation of aromatic alcohols/Suzuki coupling/asymmetric aldol reactions with excellent oxidation and coupling performance (yields up to 95 and 96%, respectively), as well as good enantioselectivities (ee_anti value up to 73%) in asymmetric aldol reactions. The heterogeneous catalyst can be reused at least five times without obvious deactivation due to the strong interaction between the MOFs and the active sites. This work provides an effective strategy to construct multifunctional catalysts via the introduction and combination of three or more of active sites, including encapsulated active species, functional organic linkers, and active metal nodes, into stable MOFs.

Synergistic Combination of Fermi Level Equilibrium and Plasmonic Effect for Formic Acid Dehydrogenation

Developing an efficient catalyst for formic acid (FA) dehydrogenation is a promising strategy for safe hydrogen storage and transportation. Herein, we successfully developed trimetallic NiAuPd heterogeneous catalysts through a galvanic replacement reaction and a subsequent chemical reduction process to boost hydrogen generation from FA decomposition at room temperature by coupling Fermi level engineering with plasmonic effect. We demonstrated that Ni worked as an electron reservoir to donate electrons to Au and Pd driven by Fermi level equilibrium whereas plasmonic Au served as an optical absorber to generate energetic hot electrons and a charge-redistribution mediator. Ni and Au worked cooperatively to promote the charge heterogeneity of surface-active Pd sites, leading to enhanced chemisorption of formate-related intermediates and eventually outstanding activity (342 mmol g^-1  h^-1 ) compared with bimetallic counterpart. This work offers excellent insight into the rational design of efficient catalysts for practical hydrogen energy exploitation.

Green synthesis of iron oxide nanoparticles derived from water and methanol extract of Centaurea solstitialis leaves and tested for antimicrobial activity and dye decolorization capability

In this research, nanoparticles derived from water extract of Centaurea solstitialis leaves were used as green adsorbent in Fenton reaction for Reactive Red 180 (RR180) and Basic Red 18 (BR18) dyes removal. At optimum operating conditions, nanoparticles proved high performance in the tested dyes removal with more than 98% of removal elimination. The free-radical scavenging, DNA nuclease, biofilm inhibition capability, antimicrobial activity, microbial cell viability, and antimicrobial photodynamic therapy activities of the iron oxide nanoparticles (FeO-NPs) derived from water and methanol extract of plant were investigated. Each of the following analysis: SEM-EDX, XRD, and Zeta potential was implemented for the prepared NPs characterization and to describe their morphology, composition and its behavior in an aqueous solution, respectively. It was found that, the DPPH scavenging activities increased when the amount of nanoparticles increased. The highest radical scavenging activity achieved with FeO-NPs derived from water extract of plant as 97.41% at 200 mg/L. The new green synthesized FeO-NPs demonstrated good DNA cleavage activity. FeO-NPs showed good in vitro antimicrobial activities against human pathogens. The results showed that both synthesized FeO-NPs displayed 100% antimicrobial photodynamic therapy activity after LED irradiation. The water extract of FeO-NPs and methanol extract of FeO-NPs also showed a significant biofilm inhibition.