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Introducing heterostructures to graphitic carbon nitrides (g-C3N4) can improve the activity of visible-light-driven catalysts for the efficient treatment of multiple toxic pollutants in water. Here, we report for the first time that a complex material can be constructed from oxygen-doped g-C3N4 and a MIL-53(Fe) metal–organic framework using facile hydrothermal synthesis and recycled polyethylene terephthalate from plastic waste. The novel multi-walled nanotube structure of the O-g-C3N4/MIL-53(Fe) composite, which enables the unique interfacial charge transfer at the heterojunction, showed an obvious enhancement in the separation efficiency of the photochemical electron–hole pairs. This resulted in a narrow bandgap energy (2.30 eV, compared to 2.55 eV in O-g-C3N4), high photocurrent intensity (0.17 mA cm−2, compared to 0.12 mA cm−2 and 0.09 mA cm−2 in MIL-53(Fe) and O-g-C3N4, respectively) and excellent catalytic performance in the photodegradation of anionic azo dyes (95% for RR 195 and 99% for RY 145 degraded after 4 h, and only a minor change in the efficiency observed after four consecutive tests). These results demonstrate the development of new catalysts made from waste feedstocks that show high stability, ease of fabrication and can operate in natural light for environmental remediation. [ABSTRACT FROM AUTHOR]

Chabazite (CHA), one of the most common zeolite framework types, has a remarkable capacity to accommodate a wide range of different cations within the unique CHA framework. This has led to CHA being applied extensively in ion exchange, and studied for highly selective gas sorption, most notably through a trapdoor mechanism. Here, we report the systematic study of a series of six chabazite zeolites (i.e. K-CHA, Cs-CHA, Ca-CHA, Ba-CHA, Sr-CHA and Zn-CHA) obtained by subjecting the parent chabazite (KNa-CHA) to exchange operations with cations of different valences and atomic radii. These samples were examined using numerous techniques and it was found that the differences in valence and size between extra-framework cations exert a significant effect on the abundance of these cations positioned in the framework, resulting in differing nitrogen sorption ability measured in the synthesised chabazite zeolites. These findings will help to understand how the zeolite counter-cation affects the ability of the CHA material to selectively sequester and separate gases through the use of the trapdoor mechanism. [ABSTRACT FROM AUTHOR]

This work demonstrates the potential of zeolite Y supported nickel phosphide materials as highly active catalysts for the upgrading of bio-oil as an improved alternative to noble metal and transition metal sulphide systems. Our systematic work studied the effect of using different counterions (NH4+, H+, K+ and Na+) and Si/Al ratios (2.56 and 15) of the zeolite Y. It demonstrates that whilst the zeolite counterion itself has little impact on the catalytic activity of the bare Y-zeolite, it has a strong influence on the activity of the resulting nickel phosphide catalysts. This effect is related to the nature of the nickel phases formed during the synthesis process Zeolites containing K+ and Na+ favour the formation of a mixed Ni12P5/Ni2P phase, H+ Y produces both Ni2P and metallic Ni, whereas NH4+ Y produces pure Ni2P, which can be attributed to the strength of the phosphorus–aluminium interaction and the metal reduction temperature. Using quinoline as a model for the nitrogen-containing compounds in bio-oils, it is shown that the hydrodenitrogenation activity increases in the order Ni2P ＞ Ni0 ＞ Ni12P5. While significant research has been dedicated to the development of bio-oils produced by thermal liquefaction of biomass, surprisingly little work has been conducted on the subsequent catalytic upgrading of these oils to reduce their heteroatom content and enable processing in conventional petrochemical refineries. This work provides important insights for the design and deployment of novel active transition metal catalysts to enable the incorporation of bio-oils into refineries. [ABSTRACT FROM AUTHOR]

Three highly porous Zr(iv)-based metal–organic frameworks, UBMOF-8, UBMOF-9, and UBMOF-31, were synthesized by using 2,2′-diamino-4,4′-stilbenedicarboxylic acid, 4,4′-stilbenedicarboxylic acid, and combination of both linkers, respectively. The mixed-linker UBMOF-31 showed excellent hydrogen uptake of 4.9 wt% and high selectivity for adsorption of CO2 over N2 with high thermal stability and moderate water stability with permanent porosity and surface area of 2552 m2 g−1. [ABSTRACT FROM AUTHOR]

Improvements in the efficiency of combustion within a vehicle can lead to reductions in the emission of harmful pollutants and increased fuel efficiency. Gas sensors have a role to play in this process, since they can provide real time feedback to vehicular fuel and emissions management systems as well as reducing the discrepancy between emissions observed in factory tests and ‘real world’ scenarios. In this review we survey the current state-of-the-art in using porous materials for sensing the gases relevant to automotive emissions. Two broad classes of porous material – zeolites and metal–organic frameworks (MOFs) – are introduced, and their potential for gas sensing is discussed. The adsorptive, spectroscopic and electronic techniques for sensing gases using porous materials are summarised. Examples of the use of zeolites and MOFs in the sensing of water vapour, oxygen, NOx, carbon monoxide and carbon dioxide, hydrocarbons and volatile organic compounds, ammonia, hydrogen sulfide, sulfur dioxide and hydrogen are then detailed. Both types of porous material (zeolites and MOFs) reveal great promise for the fabrication of sensors for exhaust gases and vapours due to high selectivity and sensitivity. The size and shape selectivity of the zeolite and MOF materials are controlled by variation of pore dimensions, chemical composition (hydrophilicity/hydrophobicity), crystal size and orientation, thus enabling detection and differentiation between different gases and vapours. [ABSTRACT FROM AUTHOR]

The potential of neutron powder diffraction (NPD) to provide vital information on the determination of accurate hydrogen positions in organic molecular crystals is demonstrated through the study of a series of hydrogen bonded molecular complexes with relevance in crystal engineering. By studying complexes designed to contain short, strong hydrogen bonds, the findings are shown to be of particular importance in the study of proton transfer, and the often critical distinction between neutral complexes and salts in these molecular materials. The use of combined NPD and single crystal X-ray diffraction is shown to be particularly potent in this area. [ABSTRACT FROM AUTHOR]

Hydrogen forms more compounds than any other element in the Periodic Table, yet methods for accurately, precisely and rapidly determining its position in a crystal structure are not readily available. The latest generation of high-flux neutron powder diffractometers, operating under optimised collection geometries, allow hydrogen positions to be extracted from the diffraction patterns of polycrystalline hydrogenous compounds without resorting to isotopic substitution. Neutron powder diffraction for hydrogenous materials has a wide range of applications within chemistry. These include the study of hydrogen-energy materials, coordination and organometallic compounds, hydrogen-bonded structures and ferroelectrics, geomaterials, zeolites and small molecule organics, such as simple sugars and amino acids. The technique is particularly well suited to parametric studies, for example as a function of temperature or pressure, where changes in hydrogen bonding patterns or decompositions involving hydrogen-containing molecules, such as water, are monitored. [ABSTRACT FROM AUTHOR]

A controlled-humidity sample environment has been constructed, allowing bulk powder samples undergoing humidity-induced phase transitions and reactions to be studied via in situ neutron diffraction. Associated developments in data collection and analysis permit this to be achieved without the use of D2O. [ABSTRACT FROM AUTHOR]

This study delves into the advanced integration of a ternary heterogeneous Z-scheme photocatalyst, TiO 2 /CuInS 2 /OCN (OCN: O-g-C 3 N 4 ), with carbon quantum dot (CQD) to improve the degradation efficiency of reactive yellow 145 (RY145) dye in water. Through a systematic examination, we elucidated the photocatalytic mechanisms and the role of radicals, electrons, and holes in the treatment process. Our findings revealed that this novel catalyst integration significantly boosted RY145 degradation efficiency, achieving 98.2%, which is markedly higher than the efficiencies which could be achieved using TiO 2 /CuInS 2 /OCN alone. Moreover, the TiO 2 /CuInS 2 /OCN/CQD photocatalyst demonstrated superior rate performance over its components. Comprehensive evaluations, including photoelectrochemical and radical tests, further confirmed the efficiency of the integrated system, adhering to Z-scheme principles. The catalyst showcased remarkable stability, with over 94% reusability after five reaction cycles. These findings pave the way for the potential use of the TiO 2 /CuInS 2 /OCN/CQD photocatalyst as an innovative solution for water pollutant treatment via photocatalytic technology., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

We demonstrate the extent to which modern detector technology, coupled with a high flux constant wavelength neutron source, can be used to obtain high quality diffraction data from short data collections, allowing the refinement of the full structures (including hydrogen positions) of hydrous compounds from in situ neutron powder diffraction measurements. The in situ thermodiffractometry and controlled humidity studies reported here reveal that important information on the reorientations of structural water molecules with changing conditions can be easily extracted, providing insight into the effects of hydrogen bonding on bulk physical properties. Using crystalline BaCl2·2H2O as an example system, we analyse the structural changes in the compound and its dehydration intermediates with changing temperature and humidity levels to demonstrate the quality of the dynamic structural information on the hydrogen atoms and associated hydrogen bonding that can be obtained without resorting to sample deuteration.

Historically the extraction of high-quality crystallographic information from inorganic samples having high hydrogen contents, such as metal hydrides, has involved preparing deuterated samples prior to study using neutron powder diffraction. We demonstrate, through direct comparison of the crystal structure refinements of the binary hydrides SrH(2) and BaH(2) with their deuteride analogues at 2 K and as a function of temperature, that precise and accurate structural information can be obtained from rapid data collections from samples containing in excess of 60 at.% hydrogen using modern high-flux, medium resolution, continuous wavelength neutron powder diffraction instruments. Furthermore, observed isotope-effects in the extracted lattice parameters and atomic positions illustrate the importance of investigating compounds in their natural hydrogenous form whenever possible.