The heptazine-based polymer melon (also known as graphitic carbon nitride, g-C3N4), is a promising photocatalyst for hydrogen evolution. Nonetheless, attempts to improve its inherently low activity are rarely based on rational approaches due lack of fundamental understanding mechanistic operation. Here, we employ molecular model catalysts identify the cyanamide moiety photocatalytically relevant "defect". We exploit this knowledge design nitride populated with groups, yielding material 12-...

A new phosphonate metal-organic framework (MOF) with a layered motif but not that of the classical hybrid inorganic-organic solid is presented. Zn(3)(L)(H(2)O)(2)·2H(2)O (L = [1,3,5-benzenetriphosphonate](6-)), henceforth denoted as PCMOF-3, contains polar interlayer lined Zn-ligated water molecules and oxygen atoms. These groups serve to anchor free into ordered chains, observed by X-ray crystallography. The potential for proton conduction via well-defined was studied (2)H solid-state NMR...

CO2 in, CH4 out! From NMR spectroscopic measurements of composition and kinetics, it can be shown that the recovery methane from hydrate is possible through its reaction with (see diagram), even though yield less than expected kinetic thermodynamic arguments. The discovery vast hydrocarbon resources in form on continental margins permafrost regions has sparked an interest relatively clean-burning gas,1 especially resource-poor national economies. At same time, been proposed CO2, obtained as...

Covalent organic frameworks (COFs) are a new class of nanoporous polymeric vector showing promise as drug-delivery vehicles with high loading capacity and biocompatibility. The interaction between the carrier cargo is specifically tailored on molecular level by H-bonding. Cell-proliferation studies indicate higher efficacy drug in cancer cells nanocarrier delivery mediated COF.

The primary amine groups on the heptazine‐based polymer melon, also known as graphitic carbon nitride (g‐C 3 N 4 ), can be replaced by urea using a two‐step postsynthetic functionalization. Under simulated sunlight and optimum Pt loading, this urea‐functionalized has one of highest activities among organic polymeric photocatalysts for hydrogen evolution with methanol sacrificial donor, reaching an apparent quantum efficiency 18% nearly 30 times rate compared to nonfunctionalized counterpart....

Abstract By applying a multitude of experimental techniques including 1 H, 14 N, 207 Pb NMR and 127 I NMR/NQR, tracer diffusion, reaction cell doping experiments, as well stoichiometric variation, conductivity, polarization iodine ions are unambiguously shown to be the mobile species in CH 3 NH PbI , with vacancies represent mechanistic centers under equilibrium conditions. 2+ + do not significantly contribute long range transport (upper limits for their contributions given), whereby latter...

Solving the structure of carbon nitrides has been a long-standing challenge due to low crystallinity and complex structures observed within this class earth-abundant photocatalysts. Herein, we report on two-dimensional layered potassium poly(heptazine imide) (K-PHI) its proton-exchanged counterpart (H-PHI), obtained by ionothermal synthesis using molecular precursor route. We present comprehensive analysis in-plane three-dimensional PHI. Transmission electron microscopy solid-state NMR...

Covalent organic frameworks (COFs) are typically designed by breaking down the desired network into feasible building blocks - either simple and highly symmetric, or more convoluted thus less symmetric. The linkers chosen complementary to each other such that an extended, fully condensed structure can form. We show not only exception, but a design principle allows free of rules. tri- tetratopic be combined form imine-linked [4 + 3] sub-stoichiometric 2D COFs featuring unexpected bex net...

Covalent organic frameworks have emerged as a powerful synthetic platform for installing and interconverting dedicated molecular functions on crystalline polymeric backbone with atomic precision. Here, we present novel strategy to directly access amine-linked covalent frameworks, which serve scaffold enabling pore-wall modification linkage-interconversion by new methods based Leuckart-Wallach reduction formic acid ammonium formate. Frameworks connected entirely secondary amine linkages,...

Substitution of vanadium into the framework mesoporous MCM-41 molecular sieves has been achieved; these materials were found to be very efficient catalysts for selective oxidation large organic molecules using hydrogen peroxide.

Thermodynamic measurements and NMR spectroscopic analysis were used to show that it is possible recover CO2 from flue gas by forming a mixed hydrate removes preferentially CO2/N2 mixtures using water dispersed in the pores of silica gel. Kinetic studies with 1H microimaging showed gel pore system reacts readily gas, thus obviating need for stirred reactor excess water. Hydrate phase equilibria ternary CO2−N2−water measured, which three-phase hydrate−water-rich liquid−vapor equilibrium curves...

Structural determination of crystalline powders, especially those complex materials, is not a trivial task. For non-stoichiometric guest-host the difficulty lies in how to determine dynamical disorder and partial cage occupancies guest molecules without other supporting information or constraints. Here, we show direct space methods combined with Rietveld analysis can be applied class host-guest this case clathrate hydrates. We report crystal structures three important hydrate classes, sI,...

Periodic mesoporous organosilicas with two-dimensional and three-dimensional hexagonal as well cubic (Pm3n) symmetry were synthesized using bridged silsesquioxane species (RO)3Si−CH2−CH2−Si(RO)3 precursors cetyl- or octadecyltrimethylammonium chloride (C16TMACl C18TMACl) structure-directing species. These materials characterized by N2 adsorption, SEM, TEM, solid-state MAS NMR spectroscopy. 13C 29Si data showed unambiguously that all carbon atoms covalently linked to Si. The material obtained...

The early age-hydration of tricalcium silicate, the main chemical compound in Portland cement, was studied presence synthetic calcium silicate hydrate (C–S–H) addition having C/S ratios = 0.8 and 1.2. Isothermal conduction calorimetry, scanning electron microscopy, differential calorimetry 29Si MAS NMR were employed order to investigate events occurring during various stages hydration. results that analyzed using novel methods cement chemistry showed seeds C–S–H significantly accelerated...

The formation of methane hydrate in an unconsolidated bed silica sand was investigated and spatially resolved by employing the magnetic resonance imaging technique. Different particle size ranges (210–297, 125–210, 88–177, <75 μm) different initial water saturations (100, 75, 50, 25%) were used. It observed that such porous media is not uniform, nucleation crystals occurs at times positions inside bed. Also, found to be faster a with lower content smaller size. Decomposition thermal...

Abstract The kinetics of gas hydrate growth from binary CH 4 /C 2 H 6 and 3 8 ternary mixtures were obtained by the uptake method in a semibatch stirred vessel at constant pressure temperature 273.7 K. These data are interest for design facilities natural storage transportation solid (hydrate) state. During formation, samples phase taken analyzed chromatography. It was found that molar composition vapor increased as crystallization progressed. observed fractionation effect (enrichment with...

Abstract Gas hydrates from a (40/60 mol %) CO 2 /H mixture, and (38.2/59.2/2.6 /C 3 H 8 were synthesized using ice powder. The gas uptake curves determined pressure drop measurements samples analyzed spectroscopic techniques to identify the structure determine cage occupancies. Powder X‐ray diffraction (PXRD) analysis at −110°C was used crystal structure. From PXRD measurement it found that hydrate is I shows self‐preservation behavior similar of hydrate. ternary mixture form pure II 3.8...

Abstract Carbon nitrides constitute a class of earth‐abundant polymeric semiconductors, which have high potential for tunability on molecular level, despite their chemical and thermal inertness. Here the first postsynthetic modification 2D carbon nitride poly(heptazine imide) (PHI) is reported, decorated with terminal melamine (Mel) moieties by functional group interconversion. The covalent attachment this verified based suite spectroscopic microscopic techniques supported quantum–chemical...

In this study, the kinetics of methane replacement with carbon dioxide and nitrogen gas in hydrate prepared porous silica gel matrices has been studied by situ (1)H (13)C NMR spectroscopy. The process was monitored spectra, where about 42 mol % cages replaced 65 h. Large amounts free water were not observed during process, indicating a spontaneous reaction upon exposing to mixture. From we confirmed that ratio slightly higher small cages, but due composition structure I hydrate, amount...

One of the best-known uses methanol is as antifreeze. Methanol used in large quantities industrial applications to prevent methane clathrate hydrate blockages from forming oil and gas pipelines. also assigned a major role antifreeze giving icy planetary bodies (e.g., Titan) liquid subsurface ocean and/or an atmosphere containing significant methane. In this work, we reveal previously unverified for guest cages. X-ray diffraction (XRD) NMR experiments showed that at temperatures near 273 K,...

We report a new lattice structure of the ionic clathrate hydrate tetra-n-butylammonium bromide induced by guest CO2 molecules, which is found to provide high storage capacity. The was characterized set methods, including single crystal X-ray diffraction, NMR, and MD simulations.

Abstract The carbon nitride poly(heptazine imide), PHI, has recently emerged as a powerful 2D photocatalyst with intriguing charge storing ability. Yet, insights into how morphology, particle size, and defects influence its photophysical properties are virtually absent. Here, ultrasonication is used to systematically tune the size well concentration of surface functional groups study their impact. Enhanced photocatalytic activity correlates an optimal amount those that create shallow trap...