Photoelectrochemical Two-Dimensional Electronic Spectroscopy (PEC2DES) of Photosystem I: Charge Separation Dynamics Hidden in a Multichromophoric Landscape

We present a nonlinear spectroelectrochemical technique to investigate photosynthetic protein complexes. The PEC2DES setup combines photoelectrochemical detection (PEC) that selectively probes the protein photogenerated charges output with two-dimensional electronic spectroscopy (2DES) excitation that spreads the nonlinear optical response of the system in an excitation-detection map. PEC allows us to distinguish the contribution of charge separation (CS) from other de-excitation pathways, whereas 2DES allows us to disentangle congested spectral bands and evaluate the exciton dynamics (decays and coherences) of the photosystem complex. We have developed in operando phase-modulated 2DES by measuring the photoelectrochemical reaction rate in a biohybrid electrode functionalized with a plant photosystem complex I-light harvesting complex I (PSI-LHCI) layer. Optimizing the photoelectrochemical current signal yields reliable linear spectra unequivocally associated with PSI-LHCI. The 2DES signal is validated by nonlinear features like the characteristic vibrational coherence at 750 cm-1. However, no energy transfer dynamics is observed within the 450 fs experimental window. These intriguing results are discussed in the context of incoherent mixing resulting in reduced nonlinear contrast for multichromophoric complexes, such as the 160 chlorophyll PSI. The presented PEC2DES method identifies generated charges unlike purely optical 2DES and opens the way to probe the CS channel in multichromophoric complexes.

Engineered Nanoporous Frameworks for Adsorption Cooling Applications

The energy demand for traditional vapor-compressed technology for space cooling continues to soar year after year due to global warming and the increasing human population's need to improve living and working conditions. Thus, there is a growing demand for eco-friendly technologies that use sustainable or waste energy resources. This review discusses the properties of various refrigerants used for adsorption cooling applications followed by a brief discussion on the thermodynamic cycle. Next, sorbents traditionally used for cooling are reviewed to emphasize the need for advanced capture materials with superior properties to improve refrigerant sorption. The remainder of the review focus on studies using engineered nanoporous frameworks (ENFs) with various refrigerants for adsorption cooling applications. The effects of the various factors that play a role in ENF-refrigerant pair selection, including pore structure/dimension/shape, morphology, open-metal sites, pore chemistry and possible presence of defects, are reviewed. Next, in-depth insights into the sorbent-refrigerant interaction, and pore filling mechanism gained through a combination of characterization techniques and computational modeling are discussed. Finally, we outline the challenges and opportunities related to using ENFs for adsorption cooling applications and provide our views on the future of this technology.

High Reactivity of Dimethyl Ether Activated by Zeolite Ferrierite within a Fer Cage: A Prediction Study

The zeolite-catalyzed conversion of DME into chemicals is considered environmentally friendly in industry. The periodic density functional theory, statistical thermodynamics, and the transition state theory are used to study some possible parallel reactions about the hydrogen-bonded DME over zeolite ferrierite. The following are the key findings: (1) the charge separation probably leads to the conversion of a hydrogen-bonded DME into a dimethyl oxonium ion (i.e., DMO+ or (CH3)2OH+) with a positive charge of about 0.804 e; (2) the methylation of DME, CH3OH, H2O, and CO by DMO+ at the T2O6 site of zeolite ferrierite shows the different activated internal energy (∆E≠) ranging from 18.47 to 30.06 kcal/mol, implying the strong methylation ability of DMO+; (3) H-abstraction by DMO+ is about 3.94-15.53 or 6.57-18.16 kcal/mol higher than DMO+ methylation in the activation internal energy; (4) six DMO+-mediated reactions are more likely to occur due to the lower barriers, compared to the experimental barrier (i.e., 39.87 kcal/mol) for methyl acetate synthesis; (5) active intermediates, such as (CH3)3O+, (CH3)2OH+, CH3CO+, CH3OH2+, and CH2=OH+, are expected to appear; (6) DMO+ is slightly weaker than the well-known surface methoxy species (ZO-CH3) in methylation; and (7) the methylated activity declines in the order of DME, CH3OH, H2O, and CO, with corresponding rate constants at 463.15 K of about 3.4 × 104, 1.1 × 102, 0.18, and 8.2 × 10-2 s-1, respectively.

Understanding ZIF particle chemical etching dynamics and morphology manipulation: in situ liquid phase electron microscopy and 3D electron tomography application

In situ liquid phase transmission electron microscopy (TEM) and three-dimensional electron tomography are powerful tools for investigating the growth mechanism of MOFs and understanding the factors that influence their particle morphology. However, their combined application to the study of MOF etching dynamics is limited due to the challenges of the technique such as sample preparation, limited field of view, low electron density, and data analysis complexity. In this research, we present a study employing in situ liquid phase TEM to investigate the etching mechanism of colloidal zeolitic imidazolate framework (ZIF) nanoparticles. The etching process involves two distinct stages, resulting in the development of porous structures as well as partially and fully hollow morphologies. The etching process is induced by exposure to an acid solution, and both in situ and ex situ experiments demonstrate that the outer layer etches faster leading to overall volume shrinking (stage I) while the inner layer etches faster giving a hollow morphology (stage II), although both the outer layer and inner layer have been etched in the whole process. 3D electron tomography was used to quantify the properties of the hollow structures which show that the ZIF-67 crystal etching rate is larger than that of the ZIF-8 crystal at the same pH value. This study provides valuable insights into MOF particle morphology control and can lead to the development of novel MOF-based materials with tailored properties for various applications.

Shaking Things from the Ground-Up: A Systematic Overview of the Mechanochemistry of Hard and High-Melting Inorganic Materials

We provide a systematic overview of the mechanochemical reactions of inorganic solids, notably simple binary compounds, such as oxides, nitrides, carbides, sulphides, phosphides, hydrides, borides, borane derivatives, and related systems. Whereas the solid state has been traditionally considered to be of little synthetic value by the broader community of synthetic chemists, the solid-state community, and in particular researchers focusing on the reactions of inorganic materials, have thrived in building a rich and dynamic research field based on mechanically-driven transformations of inorganic substances typically seen as inert and high-melting. This review provides an insight into the chemical richness of such mechanochemical reactions and, at the same time, offers their tentative categorisation based on transformation type, resulting in seven distinct groupings: (i) the formation of adducts, (ii) the reactions of dehydration; (iii) oxidation-reduction (redox) reactions; (iv) metathesis (or exchange) reactions; (v) doping and structural rearrangements, including reactions involving the reaction vessel (the milling jar); (vi) acid-base reactions, and (vii) other, mixed type reactions. At the same time, we offer a parallel description of inorganic mechanochemical reactions depending on the reaction conditions, as those that: (i) take place under mild conditions (e.g., manual grinding using a mortar and a pestle); (ii) proceed gradually under mechanical milling; (iii) are self-sustained and initiated by mechanical milling, i.e., mechanically induced self-propagating reactions (MSRs); and (iv) proceed only via harsh grinding and are a result of chemical reactivity under strongly non-equilibrium conditions. By elaborating on typical examples and general principles in the mechanochemistry of hard and high-melting substances, this review provides a suitable complement to the existing literature, focusing on the properties and mechanochemical reactions of inorganic solids, such as nanomaterials and catalysts.

High performance supercapacitors based on wood-derived thick carbon electrodes synthesized via green activation process

A green, versatile, and universal H2O2 activation method is proposed to improve the capacitive properties of high-mass loading wood-based supercapacitors.