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Communities downstream from mountainous regions rely on snowmelt for water supply. As climate change reduces the reliability of the snowpack in these regions it is important to understand how and when rain and melt water are stored and released as runoff. In mountainous regions the prediction of water movement is especially complex because water storage capacity and overall water input magnitude and form vary over short distances given variable geology, geomorphology, and topography. We used water stable isotopes (WSI) and water chemistry (ions and cations) to investigate seasonal water sources and contributions in a 64 km2 headwater mountain catchment in Oregon (USA). In one study, we collected > 1,000 synoptic samples between 2021 and 2022 across different seasons in 12 headwater streams (600–1,200 m in elevation and drainage areas 0.1–5 km2) and analyzed them for WSI. Results demonstrate that despite season there are localized variations in WSI within less than 1-km2 between catchments underlain by similar geology but characterized by different geomorphic history of mass wasting events (landslides and earthflows). We also observed weak relationships between elevation and WSI in some streams suggesting that their sources of baseflow are not directly controlled by seasonal precipitation but by differences in storage over spatially variability geomorphic history. In a second study, we investigated relative streamflow contributions from five tributaries (0.7–17 km2) over the whole year based on weekly WSI and water chemistry in grab and precipitation samples. We found strong differences across streams; the most interesting was a spring-fed stream, whose water contribution varies widely throughout the year, resembling a snowmelt system (with high relative water input in the summer). The depleted WSI signal and relatively high cations concentrations of this stream reveals higher elevation snowfall is moving to the stream through relatively long flow paths. This stream is underlain by porous lava flows demonstrating a strong geologic control on runoff generation. The contribution of this stream to the whole watershed is over 27 times larger in the summer compared to any other season. This finding challenges the idea of streamflow scaling with drainage area because the effective drainage area of this stream varies between 0.8 and 47 km2 while the topographic derived drainage area is 0.7 km2.

Thermal decomposition of an iron-based MOF was conducted under controlled gas environments to understand the resulting porous carbon structure. Different phases and crystallite sizes of iron oxide are produced based on the specific gas species. In particular, air resulted in iron(III) oxide, and D2O and CO2 resulted in the mixed valent iron(II,III) oxide. Performing the carbonization under non-oxidative or reducing conditions (N2, He, H2) resulted in the formation of a mixture of both iron(II,III) oxide and iron(III) oxide. Based on in situ and air-free handling experiments, it was observed that this is partially due to the formation of zero-valent iron metal that is rapidly oxidized when exposed to air. Neutron pair distribution function analysis provided insight into the effect of the gas environment on the local structure of the porous carbon, indicating a noticeable change in local order between the D2O and the N2 calcined samples.

Investigations into a thermally generated decarboxylation mechanism for metal site activation and the generation of mesopores in a carboxylate iron-based MOF, PCN-250, have been conducted. PCN-250 exhibits an interesting oxidation state change during thermal treatment under inert atmospheres or vacuum conditions, transitioning from an Fe(III)(3) cluster to a Fe(II)Fe(III)(2) cluster. To probe this redox event and discern a mechanism of activation, a combination of thermogravimetric analysis, gas sorption, scanning electron microscopy, (57)Fe Mössbauer spectroscopy, gas chromatography-mass spectrometry, and X-ray diffraction studies were conducted. The results suggest that the iron-site activation occurs due to ligand decarboxylation above 200 °C. This is also consistent with the generation of a missing cluster mesoporous defect in the framework. The resulting mesoporous PCN-250 maintains high thermal stability, preserving crystallinity after multiple consecutive high-temperature regeneration cycles. Additionally, the thermally reduced PCN-250 shows improvements in the total uptake capacity of methane and CO(2).

Four-fold interpenetrating framework 1a can be constructed driven by temperature-controlled SC-SC transformation from 2-fold interpenetrating network 1. Luminescent properties indicated that 1a can be viewed as a luminescent sensor of high-explosives.

Thermal decomposition of an iron-based MOF was conducted under controlled gas environments to understand the resulting porous carbon structure. Different phases and crystallite sizes of iron oxide are produced based on the specific gas species. In particular, air results in iron(III) oxide, and D2O and CO2 results in the mixed valent iron (II,III) oxide. Performing the carbonization under non-oxidative or reducing conditions (N2, He, H2) results in the formation of a mixture of both iron (II,III) oxide and iron (III) oxide. Based on in situ and air free handling experiments, it was observed that this is partially due to the formation of zero-valent iron metal that is rapidly oxidized when exposed to air. Neutron pair distribution function analysis provided insight into the effect of the gas environment on the local structure of the porous carbon, indicating a noticeable change in local order between the D2O and the N2 calcined samples.

Natural enzymes catalyze reactions in their substrate-binding cavities, exhibiting high specificity and efficiency. In an effort to mimic the structure and functionality of enzymes, discrete coordination cages were designed and synthesized. These self-assembled systems have a variety of confined cavities, which have been applied to accelerate conventional reactions, perform substrate-specific reactions, and manipulate regio- and enantio-selectivity. Many coordination cages or cage-catalyst composites have achieved unprecedented results, outperforming their counterparts in different catalytic reactions. This tutorial review summarizes recent developments of coordination cages across three key approaches to coordination cage catalysis: (1) cavity promoted reactions, (2) embedding of active sites in the structure of the cage, and (3) encapsulation of catalysts within the cage. Special emphasis of the review involves (1) introduction of the structure and property of the coordination cage, (2) discussion of the catalytic pathway mediated by the cage, (3) elucidation of the structure-property relationship between the cage and the designated reaction. This work will summarize the recent progress in supramolecular catalysis and attract more researchers to pursue cavity-promoted reactions using discrete coordination cages.

In order to determine a material's hydrogen storage potential, capacity measurements must be robust, reproducible, and accurate. Commonly, research reports focus on the gravimetric capacity, and often times the volumetric capacity is not reported. Determining volumetric capacities is not as straight-forward, especially for amorphous materials. This is the first study to compare measurement reproducibility across laboratories for excess and total volumetric hydrogen sorption capacities based on the packing volume. The use of consistent measurement protocols, common analysis, and figure of merits for reporting data in this study, enable the comparison of the results for two different materials. Importantly, the results show good agreement for excess gravimetric capacities amongst the laboratories. Irreproducibility for excess and total volumetric capacities is attributed to real differences in the measured packing volume of the material.

Adsorbents for CO2 capture need to demonstrate efficient release. Light-induced swing adsorption (LISA) is an attractive new method to release captured CO2 that utilizes solar energy rather than electricity. MOFs, which can be tailored for use in LISA owing to their chemical functionality, are often unstable in moist atmospheres, precluding their use. A MOF is used that can release large quantities of CO2 via LISA and is resistant to moisture across a large pH range. PCN-250 undergoes LISA, with UV flux regulating the CO2 desorption capacity. Furthermore, under UV light, the azo residues within PCN-250 have constrained, local, structural flexibility. This is dynamic, rapidly switching back to the native state. Reusability tests demonstrate a 7.3 % and 4.9 % loss in both adsorption and LISA capacity after exposure to water for five cycles. These minimal changes confirm the structural robustness of PCN-250 and its great potential for triggered release applications.

Nature has evolved a great number of biological molecules which serve as excellent constructional or functional units for metal–organic materials (MOMs). Even though the study of biomimetic MOMs is still at its embryonic stage, considerable progress has been made in the past few years. In this critical review, we will highlight the recent advances in the design, development and application of biomimetic MOMs, and illustrate how the incorporation of biological components into MOMs could further enrich their structural and functional diversity. More importantly, this review will provide a systematic overview of different methods for rational design of MOMs with biomimetic features.

A series of molybdenum- and copper-based MOPs were synthesized through coordination-driven process of a bridging ligand (3,3'-PDBAD, L(1)) and dimetal paddlewheel clusters. Three conformers of the ligand exist with an ideal bridging angle between the two carboxylate groups of 0° (H2α-L(1)), 120° (H2β-L(1)), and of 90° (H2γ-L(1)), respectively. At ambient or lower temperature, H2L(1) and Mo2(OAc)4 or Cu2(OAc)4 were crystallized into a molecular square with γ-L(1) and Mo2/Cu2 units. With proper temperature elevation, not only the molecular square with γ-L(1) but also a lantern-shaped cage with α-L(1) formed simultaneously. Similar to how Watson-Crick pairs stabilize the helical structure of duplex DNA, the core-shell molecular assembly possesses favorable H-bonding interaction sites. This is dictated by the ligand conformation in the shell, coding for the formation and providing stabilization of the central lantern shaped core, which was not observed without this complementary interaction. On the basis of the crystallographic implications, a heterobimetallic cage was obtained through a postsynthetic metal ion metathesis, showing different reactivity of coordination bonds in the core and shell. As an innovative synthetic strategy, the site-selective metathesis broadens the structural diversity and properties of coordination assemblies.

Herein we report for the first time the synthesis of Cr(II)-based metal–organic polyhedra (MOPs) and the characterization of their porosities. Unlike the isostructural Cu(II)- or Mo(II)-based MOPs, Cr(II)-based MOPs show unusually high gas uptakes and surface areas. The combination of comparatively robust dichromium paddlewheel units (Cr2 units), cage symmetries, and packing motifs enable these materials to achieve Brunauer–Emmett–Teller surface areas of up to 1000 m2/g. Reducing the aggregation of the Cr(II)-based MOPs upon activation makes their pores more accessible than their Cu(II) or Mo(II) counterparts. Further comparisons of surface areas on a molar (m2/mol cage) rather than gravimetric (m2/g) basis is proposed as a rational method of comparing members of a family of related molecular materials.

Stimuli-responsive metal-organic polyhedra (srMOPs) functionalized with azobenzene showed UV-irradiation-induced isomerization from the insoluble trans-srMOP to the soluble cis-srMOP, whereas irradiation with blue light reversed this process. Guest molecules were trapped and released upon cis-to-trans and trans-to-cis isomerization of the srMOPs, respectively. This study provides a new direction in the ever-diversifying field of MOPs, while laying the groundwork for a new class of optically responsive materials.

Porous Polymer Networks (PPNs) are an emerging category of advanced porous materials that are of interest for carbon dioxide capture due to their great stabilities and convenient functionalization processes. In this work, an intrinsically-functionalized porous network, PPN-101, was prepared from commercially accessible materials via an easy two-step synthesis. It has a BET surface area of 1095 m2/g. Due to the presence of the benzimidazole units in the framework, its CO2 uptake at 273 K reaches 115 cm3/g and its calculated CO2/N2 selectivity is 199, which indicates its potential for CO2/N2 separation. The great stability, large CO2/N2 selectivity and low production cost make PPN-101 a promising material for industrial separation of CO2 from flue gas. Its H2 and CH4 uptake properties were also investigated.

Nature has evolved a great number of biological molecules which serve as excellent constructional or functional units for metal–organic materials (MOMs). Even though the study of biomimetic MOMs is still at its embryonic stage, considerable progress has been made in the past few years. In this critical review, we will highlight the recent advances in the design, development and application of biomimetic MOMs, and illustrate how the incorporation of biological components into MOMs could further enrich their structural and functional diversity. More importantly, this review will provide a systematic overview of different methods for rational design of MOMs with biomimetic features.

In pervasiveness of occurrence and multiplicity of function, iron–sulfur clusters rival biological prosthetic groups such as hemes and flavins. The development of iron–sulfur cluster chemistry paralleled the founding and maturation of the field of bioinorganic chemistry. Starting from the first spontaneous self-assembly of the [Fe4S4(SR)4]2− cluster in 1972, and the identification of the protein-bound Fe4S4 in the same year, the study of iron–sulfur models of protein active sites has evolved into a unique field in which synthetic inorganic chemistry now resembles the total synthesis of natural products in organic chemistry. Some of the models had been built before the crystal structure of the protein was determined. Almost all the models successfully replicated the topology and the electronic properties of the protein active sites. In this article, the models will be discussed in the order of their complexity, from single iron rubredoxin models to Fe2S2, Fe3S4, Fe4S4, and Fe8S7 model compounds. In each section, the chemical synthesis of the model compound will be discussed first, followed by structure comparison and contrast, electrochemical properties, and biochemical activities. Since the major function of iron–sulfur proteins is electron transfer, and the oxidation state of the iron atom determines its reactivity, electrochemical and Mossbauer data will be tabulated in detail. Some of the recent developments in site-differentiated, peptide, and all-ferrous Fe4S4 clusters will be reviewed. Recent studies in modeling the topology of the P-cluster of nitrogenase will also be covered. The challenge posed by iron–sulfur proteins has inspired new iron–sulfur cluster chemistry. No other metal–nonmetal combination has produced more structural types than the iron–sulfur system; the majority of them have yet to be found in biological systems. However, the modeling of the P-cluster and the FeMoco center of nitrogenase have posed a daunting challenge to the analog chemists. Keywords: iron–sulfur; model compounds; rubredoxin; ferredoxin; P-cluster; cubane; cuboidal; peptide model; site-differentiated; electrochemical property; Mossbauer data

One of the most pressing environmental concerns of our age is the escalating level of atmospheric CO2 . Intensive efforts have been made to investigate advanced porous materials, especially porous organic polymers (POPs), as one type of the most promising candidates for carbon capture due to their extremely high porosity, structural diversity, and physicochemical stability. This review provides a critical and in-depth analysis of recent POP research as it pertains to carbon capture. The definitions and terminologies commonly used to evaluate the performance of POPs for carbon capture, including CO2 capacity, enthalpy, selectivity, and regeneration strategies, are summarized. A detailed correlation study between the structural and chemical features of POPs and their adsorption capacities is discussed, mainly focusing on the physical interactions and chemical reactions. Finally, a concise outlook for utilizing POPs for carbon capture is discussed, noting areas in which further work is needed to develop the next-generation POPs for practical applications.