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1.
Proc Natl Acad Sci U S A ; 120(3): e2212075120, 2023 01 17.
Artículo en Inglés | MEDLINE | ID: mdl-36634137

RESUMEN

Liquid methanol has the potential to be the hydrogen energy carrier and storage medium for the future green economy. However, there are still many challenges before zero-emission, affordable molecular H2 can be extracted from methanol with high performance. Here, we present noble-metal-free Cu-WC/W plasmonic nanohybrids which exhibit unsurpassed solar H2 extraction efficiency from pure methanol of 2,176.7 µmol g-1 h-1 at room temperature and normal pressure. Macro-to-micro experiments and simulations unveil that local reaction microenvironments are generated by the coperturbation of WC/W's lattice strain and infrared-plasmonic electric field. It enables spontaneous but selective zero-emission reaction pathways. Such microenvironments are found to be highly cooperative with solar-broadband-plasmon-excited charge carriers flowing from Cu to WC surfaces for efficient stable CH3OH plasmonic reforming with C3-dominated liquid products and 100% selective gaseous H2. Such high efficiency, without any COx emission, can be sustained for over a thousand-hour operation without obvious degradation.

2.
Int J Behav Nutr Phys Act ; 21(1): 91, 2024 Aug 19.
Artículo en Inglés | MEDLINE | ID: mdl-39160546

RESUMEN

BACKGROUND: Greater public transport use has been linked to higher physical activity levels. However, neither the amount of physical activity associated with each daily public transport trip performed, nor the potential total physical activity gain associated with an increase in trips/day, has been determined. Using objective measures, we aimed to quantify the association between public transport use, physical activity and sedentary time. METHODS: A longitudinal study of Australian adults living in Hobart, Tasmania, who were infrequent bus users (≥ 18 years; used bus ≤ 2 times/week). The number of bus trips performed each day was determined from objective smartcard data provided by the public transportation (bus) provider across a 36-week study timeframe. Accelerometer measured steps/day (primary outcome), moderate-to-vigorous physical activity (min/day), and sedentary time (min/day) were assessed across four separate one-week periods. RESULTS: Among 73 participants across 1483 day-level observations, on days that public transport was used, participants achieved significantly more steps (ß = 2147.48; 95%CI = 1465.94, 2829.03), moderate to vigorous physical activity (ß = 22.79; 95% CI = 14.33, 31.26), and sedentary time (ß = 37.00; 95% CI = 19.80, 54.21) compared to days where no public transport trips were made. The largest increase in steps per day associated with a one-trip increase was observed when the number of trips performed each day increased from zero to one (ß = 1761.63; 95%CI = 821.38, 2701.87). The increase in the number of steps per day was smaller and non-significant when the number of trips performed increased from one to two (ß = 596.93; 95%CI=-585.16, 1779.01), and two to three or more (ß = 632.39; 95%CI=-1331.45, 2596.24) trips per day. Significant increases in sedentary time were observed when the number of trips performed increased from zero to one (ß = 39.38; 95%CI = 14.38, 64.39) and one to two (ß = 48.76; 95%CI = 25.39, 72.12); but not when bus trips increased from two to three or more (ß=-27.81; 95%CI=-76.00, 20.37). CONCLUSIONS: Greater public transport use was associated with higher physical activity and sedentary behaviour. Bus use may yield cumulative increases in steps that amount to 15-30% of the daily recommended physical activity target. A policy and public health focus on intersectoral action to promote public transport may yield meaningful increases in physical activity and subsequent health benefits.


Asunto(s)
Acelerometría , Ejercicio Físico , Conducta Sedentaria , Transportes , Humanos , Transportes/métodos , Masculino , Femenino , Adulto , Estudios Longitudinales , Persona de Mediana Edad , Tasmania , Australia
3.
Prev Med ; 179: 107825, 2024 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-38128768

RESUMEN

Transport-related physical activity levels differ across the lifecourse; however, the nature of these differences is poorly understood. This study examined the relationship between correlates of transport-related physical activity and how they differ in strength, pathway, and direction across the lifecourse. Structural Equation Modelling assessed relationships between correlates (e.g., age, smoking, education) and transport-related physical activity (assessed via the International Physical Activity Questionnaire) at four timepoints of the Australian Childhood Determinants of Adult Health study: childhood (7-15y; n = 6302), early-adulthood (26-36y; n = 2700), early/mid-adulthood (31-41y; n = 1649), and mid-adulthood (36-49y; n = 1794). Several pathways were consistent across the lifecourse. Self-rated health directly associated with transport-related physical activity across all timepoints. During adulthood greater body mass index and smoking frequency were indirectly associated with lower levels of transport-related physical activity via self-rated health; similarly, lower educated adults, who smoked more frequently, and had poorer health, had lower transport-related physical activity. Urban residence was directly associated with greater transport-related physical activity in childhood and early-adulthood; having more children in early/mid- and mid-adulthood was directly associated with less transport-related physical activity. This is the first study to report pathways of direct and indirect association between correlates and transport-related physical activity at key lifecourse stages. The pathways highlighted can inform policy and practice to aid in the development of age-specific lifecourse interventions.


Asunto(s)
Ejercicio Físico , Fumar , Adulto , Niño , Humanos , Análisis de Clases Latentes , Australia , Fumar/epidemiología , Escolaridad
4.
Prev Med ; 189: 108128, 2024 Sep 06.
Artículo en Inglés | MEDLINE | ID: mdl-39244160

RESUMEN

OBJECTIVE: Child and adult body mass index (BMI) associates with adult carotid artery intima-media thickness (cIMT). However, the relative contribution of BMI at different life-periods on adult cIMT has not been quantified. This study aimed to determine the life-course model that best explains the relative contribution of BMI at different life-periods (childhood, adolescence, and young-adulthood) on cIMT in adulthood. METHODS: BMI was calculated from direct measurements of height and weight at up to seven time-points from childhood to adulthood (1973-2007) among 2485 participants of the Cardiovascular Risk in Young Finns Study (YFS) and 1271 participants in the Bogalusa Heart Study (BHS). BMI measures at three ages representative of childhood (9-years), adolescence (18 years) and young-adulthood (30 years) life-periods were used. B-mode ultrasound was used to measure common cIMT in adulthood (>30 years). Associations were evaluated using the Bayesian relative life-course exposure model. RESULTS: In both cohorts, cumulative exposure to higher levels of BMI across the life-course was associated with greater cIMT. Of the examined life-periods, BMI in young-adulthood provided the greatest relative contribution towards the development of adult cIMT for YFS (49.9 %, 95 % CrI = 34-68 %) and white BHS participants (48.6 %, 95 % CrI = 9-86 %), whereas BMI in childhood had the greatest relative contribution for black BHS participants (54.0 %, 95 % CrI = 8-89 %). CONCLUSION: Although our data suggest sensitive periods in the life-course where prevention and intervention aimed at reducing BMI might provide most benefit in limiting the effects of BMI on cIMT, maintaining lower BMI across the life-course appears to be optimal.

5.
Heart Lung Circ ; 33(3): 281-291, 2024 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-38365495

RESUMEN

BACKGROUND: Chronic kidney disease (CKD) coexists in up to 50% of heart failure (HF) patients, affecting both those with reduced ejection fraction (HFrEF) and those with preserved ejection fraction (HFpEF). Although the efficacy of several guideline-directed medical therapies (GDMT) has been well established, the treatment recommendations are similar for those patients with HF with and without CKD. We aimed to investigate the efficacy of GDMT in patients with HF with versus those without CKD. METHOD: This systematic review and meta-analysis included randomised controlled trials that compared the efficacy of GDMT (angiotensin-converting enzyme inhibitor [ACE-I], beta blocker, sodium-glucose cotransporter-2 inhibitor, mineralocorticoid receptor antagonist, angiotensin receptor-neprilysin inhibitor) in patients with HF with and without CKD. The primary outcome was the composite of cardiovascular death and HF hospitalisation. Risk ratios (RR) were pooled using random-effects meta-analysis. RESULTS: A total of 19 trials (15 trials in HFrEF and four trials in HFpEF) enrolling 63,677 (38% had CKD) participants were included. Among HFrEF patients, GDMT reduced the primary endpoint in those with CKD (RR 0.77, 95% confidence interval [CI] 0.72-0.82) and without CKD (RR 0.79, 95% CI 0.74-0.84). Among HFpEF patients, the pooled summary RR for GDMT reducing the primary endpoint was 0.82 (95% CI 0.74-0.91) among those with CKD and 0.88 (95% CI 0.77-0.99) among those without CKD. There was no significant difference in the efficacy of GDMT in head-to-head comparisons between those with and without CKD in HFrEF (ratio of RR 0.97, 95% CI 0.88-1.06) and HFpEF (ratio of RR 0.94, 95% CI 0.80-1.11). CONCLUSIONS: Among patients with HF, GDMT had a consistent effect in reducing adverse cardiovascular events in those with and without CKD. Future studies should investigate the best strategy to ensure patients with HF with CKD receive and tolerate GDMT when indicated.


Asunto(s)
Insuficiencia Cardíaca , Insuficiencia Renal Crónica , Inhibidores del Cotransportador de Sodio-Glucosa 2 , Humanos , Antagonistas Adrenérgicos beta , Antagonistas de Receptores de Angiotensina/uso terapéutico , Inhibidores de la Enzima Convertidora de Angiotensina/uso terapéutico , Insuficiencia Cardíaca/complicaciones , Insuficiencia Cardíaca/tratamiento farmacológico , Insuficiencia Renal Crónica/complicaciones , Insuficiencia Renal Crónica/tratamiento farmacológico , Inhibidores del Cotransportador de Sodio-Glucosa 2/farmacología , Volumen Sistólico
6.
Angew Chem Int Ed Engl ; 63(24): e202400474, 2024 Jun 10.
Artículo en Inglés | MEDLINE | ID: mdl-38590031

RESUMEN

Metal-organic framework (MOF)-based mixed matrix membranes (MMMs) have shown great promises to overcome the performance upper limit of polymeric membranes for various gas separation processes. However, the gas separation properties of the MMMs largely depend on the MOF-polymer interfacial compatibility which is a metric difficult to quantify. In most cases, whether a MOF filler and a polymer matrix make a good pair is not revealed until the gas transport experiments are performed. This is because there is a lack of characterization techniques to directly probe the MOF-polymer interfacial compatibility. In this work, we demonstrate a self-sorting method to rank the interface compatibility among several MOF-polymer pairs. By mixing one MOF with two polymers in an MMM, the demixing of two polymers will form two polymer domains. The MOF particles will preferably partition into the "preferred" polymer domain due to their higher interfacial affinity. By scanning different polymer pairs, a rank of MOF-polymer interfacial compatibility from high to low can be obtained. Moreover, based on this ranking, it was also found that a highly compatible MOF-polymer pair suggested by this method also corresponds to a more predictable MMM gas separation performance.

7.
Heart Fail Rev ; 28(4): 949-959, 2023 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-36198840

RESUMEN

Women have been historically underrepresented in clinical trials of heart failure (HF). We aimed to assess for sex differences in patient characteristics and the efficacy of guideline-directed medical therapy (GDMT) in HF. Systematic literature search for randomized controlled trials (RCTs) of GDMT reporting cardiovascular outcomes by sex in patients with HF. The primary outcome was the composite of cardiovascular death and hospitalization for HF. Risk ratios (RR) with 95% confidence intervals (CI) were pooled using inverse variance weighting and random effects meta-analysis. Twenty-six RCTs totaling 84,818 participants (27% women) were included. Women with HF were older, had higher New York Heart Association (NYHA) class, more hypertension and obesity, and higher mean left ventricular ejection fraction compared to men. There was evidence for most GDMT in reducing the primary outcome in women with HF with reduced ejection fraction (HFrEF) (angiotensin-converting enzyme inhibitors/angiotensin-receptor blocker [RR 0.86, 95% CI 0.75-0.97], angiotensin-receptor blocker/neprilysin inhibitor (ARNI) [RR 0.77, 95% CI 0.62-0.94], beta-blocker [RR 0.67, 95% CI 0.51-0.89], ivabradine [RR 0.74, 95% CI 0.60-0.91], and sodium-glucose cotransporter-2 (SGLT2) inhibitors [RR 0.66, 95% CI 0.54-0.81]) and a non-significant trend for benefit with mineralocorticoid-receptor-antagonist (MRA) [RR 0.77, 95% CI 0.52-1.16]). Compared to men with HFrEF, GDMT reduced the primary outcome in women to a similar degree across all drug classes (ratio of RR 1.05, 95% CI 0.96-1.14). Despite differences in baseline characteristics and an underrepresentation of women in HF clinical trials, GDMT are as efficacious in women as compared to men in reducing cardiovascular events in HF.


Asunto(s)
Insuficiencia Cardíaca , Caracteres Sexuales , Masculino , Femenino , Humanos , Insuficiencia Cardíaca/tratamiento farmacológico , Ivabradina , Antagonistas de Receptores de Angiotensina , Volumen Sistólico , Angiotensinas
8.
Int J Behav Nutr Phys Act ; 20(1): 63, 2023 05 26.
Artículo en Inglés | MEDLINE | ID: mdl-37237392

RESUMEN

BACKGROUND: Transport-related physical activity (TRPA) is recognised as a potential means of increasing total physical activity participation that may yield substantial health benefits. Public health campaigns focusing on promoting TRPA from a young age aim to develop life-long healthy habits. However, few studies have examined how TRPA changes across the lifecourse and whether childhood TRPA levels influence those observed later in life. METHODS: Using the Australian Childhood Determinants of Adult Health study (baseline, 1985), latent class growth mixture modelling with adjustment for time-varying covariates was performed using four timepoints (ranging from 7 to 49 years) to assess behavioural patterns and retention of TRPA across the lifecourse. As child and adult adjusted TRPA measures could not be harmonised, trajectories of adult TRPA (n = 702) were instead identified, and log-binomial regression analysis was performed to determine whether childhood levels of TRPA (high/medium/low) influenced these trajectories. RESULTS: Two stable groups of adult TRPA trajectories were identified: persistently low (n = 520; 74.2%), and increasingly high TRPA (n = 181; 25.8%). There was no significant relationship between childhood TRPA levels and patterns in adulthood (relative risk of high childhood TRPA yielding high adult TRPA trajectory membership = 1.06; 95% confidence interval = 0.95-1.09). CONCLUSION: This study found childhood TRPA levels were not associated with TRPA patterns in adulthood. These findings suggest that while TRPA in childhood may have health, social, and environmental benefits, it does not appear to impact adult TRPA directly. Therefore, further intervention is required beyond childhood to promote the implementation of healthy TRPA behaviours into adulthood.


Asunto(s)
Ejercicio Físico , Adulto , Humanos , Australia , Estudios Longitudinales , Riesgo
9.
Int J Behav Nutr Phys Act ; 20(1): 98, 2023 08 16.
Artículo en Inglés | MEDLINE | ID: mdl-37587424

RESUMEN

BACKGROUND: Public transport users tend to accumulate more physical activity than non-users; however, whether physical activity is increased by financially incentivising public transport use is unknown. The trips4health study aimed to determine the impact of an incentive-based public transport intervention on physical activity. METHODS: A single-blinded randomised control trial of a 16-week incentive-based intervention involved Australian adults who were infrequent bus users (≥ 18 years; used bus ≤ 2 times/week) split equally into intervention and control groups. The intervention group were sent weekly motivational text messages and awarded smartcard bus credit when targets were met. The intervention group and control group received physical activity guidelines. Accelerometer-measured steps/day (primary outcome), self-reported transport-related physical activity (walking and cycling for transport) and total physical activity (min/week and MET-min/week) outcomes were assessed at baseline and follow-up. RESULTS: Due to the COVID pandemic, the trial was abandoned prior to target sample size achievement and completion of all assessments (N = 110). Steps/day declined in both groups, but by less in the intervention group [-557.9 steps (-7.9%) vs.-1018.3 steps/week (-13.8%)]. In the intervention group, transport-related physical activity increased [80.0 min/week (133.3%); 264.0 MET-min/week (133.3%)] while total physical activity levels saw little change [35.0 min/week (5.5%); 25.5 MET-min/week (1.0%)]. Control group transport-related physical activity decreased [-20.0 min/week (-27.6%); -41.3 MET-min/week (-17.3%)], but total physical activity increased [260.0 min/week (54.5%); 734.3 MET-min/week (37.4%)]. CONCLUSION: This study found evidence that financial incentive-based intervention to increase public transport use is effective in increasing transport-related physical activity These results warrant future examination of physical activity incentives programs in a fully powered study with longer-term follow-up. TRIAL REGISTRATION: This trial was registered with the Australian and New Zealand Clinical Trials Registry August 14th, 2019: ACTRN12619001136190; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=377914&isReview=true.


Asunto(s)
COVID-19 , Humanos , Adulto , Australia , Motivación , Ejercicio Físico , Caminata
10.
Inorg Chem ; 62(47): 19208-19217, 2023 Nov 27.
Artículo en Inglés | MEDLINE | ID: mdl-37963068

RESUMEN

Nanoconfinement in metal-organic framework (MOF) pores can lead to the isolation of unusual or reactive metal complexes. However, MOFs that support the stabilization and precise structural elucidation of metal complexes and small metal clusters are rare. Here, we report a thermally and chemically stable zirconium-based MOF (University of Adelaide Material-1001, UAM-1001) with a high density of free bis-pyrazolyl units that can confine mono- and dinuclear metal complexes. The precursor MOF, UAM-1000, has a high degree of structural flexibility, but post synthetic modification with a bracing linker, biphenyl-4,4'-dicarboxylic acid, partially rigidifies the MOF (UAM-1001). This allows "matrix isolation" and detailed structural elucidation of postsynthetically added dimeric complexes bound within a tetradentate binding site formed by two linkers. Dimeric species [Co2Cl4], [Cu2Cl4], [Ni2Cl3(H2O)2]Cl, and [Rh2(CO)3Cl2] were successfully isolated in UAM-1001 and characterized by single-crystal X-ray diffraction. Comparison of the UAM-1001 isolated species with similar complexes in the solid state reveals that UAM-1001 can significantly distort the structures and enforce notably shorter metal-metal distances. For example, MOF tethering allows isolation of a [Cu2Cl4] complex that rapidly reacts with water in the solid state. The stability, porosity, and modulated flexibility of UAM-1001 provide an ideal platform material for the isolation and study of new dimeric complexes and their reactivity.

11.
Angew Chem Int Ed Engl ; 62(49): e202314378, 2023 Dec 04.
Artículo en Inglés | MEDLINE | ID: mdl-37816684

RESUMEN

One of the key challenges of metallo-supramolecular chemistry is to maintain the ease of self-assembly but, at the same time, create structures of increasingly high levels of complexity. In palladium(II) quadruply stranded lantern-shaped cages, this has been achieved through either 1) the formation of heteroleptic (multi-ligand) assemblies, or 2) homoleptic assemblies from low-symmetry ligands. Heteroleptic cages formed from low-symmetry ligands, a hybid of these two approaches, would add an additional rich level of complexity but no examples of these have been reported. Here we use a system of ancillary complementary ligand pairings at the termini of cage ligands to target heteroleptic assemblies: these complementary pairs can only interact (through coordination to a single Pd(II) metal ion) between ligands in a cis position on the cage. Complementarity between each pair (and orthogonality to other pairs) is controlled by denticity (tridentate to monodentate or bidentate to bidentate) and/or hydrogen-bonding capability (AA to DD or AD to DA). This allows positional and orientational control over ligands with different ancillary sites. By using this approach, we have successfully used low-symmetry ligands to synthesise complex heteroleptic cages, including an example with four different low-symmetry ligands.

12.
Virtual Real ; : 1-16, 2023 May 06.
Artículo en Inglés | MEDLINE | ID: mdl-37360802

RESUMEN

Circle drawing may be a useful task to study upper-limb function in patient populations. However, previous studies rely on expensive and bulky robotics to measure performance. For clinics or hospitals with limited budgets and space, this may be unfeasible. Virtual reality (VR) provides a portable and low-cost tool with integrated motion capture. It offers potentially a more feasible medium by which to assess upper-limb motor function. Prior to use with patient populations, it is important to validate and test the capabilities of VR with healthy users. This study examined whether a VR-based circle drawing task, completed remotely using participant's own devices, could capture differences between movement kinematics of the dominant and non-dominant hands in healthy individuals. Participants (n = 47) traced the outline of a circle presented on their VR head-mounted displays with each hand, while the positions of the hand-held controllers were continuously recorded. Although there were no differences observed in the size or roundness of circles drawn with each hand, consistent with prior literature our results did show that the circles drawn with the dominant hand were completed faster than those with the non-dominant hand. This provides preliminary evidence that a VR-based circle drawing task may be a feasible method for detecting subtle differences in function in clinical populations. Supplementary Information: The online version contains supplementary material available at 10.1007/s10055-023-00794-z.

13.
Chemistry ; 28(55): e202201281, 2022 Oct 04.
Artículo en Inglés | MEDLINE | ID: mdl-35802315

RESUMEN

DUT-8(Ni) metal-organic framework (MOF) belongs to the family of flexible pillared layer materials. The desolvated framework can be obtained in the open pore form (op) or in the closed pore form (cp), depending on the crystal size regime. In the present work, we report on the behaviour of desolvated DUT-8(Ni) at elevated temperatures. For both, op and cp variants, heating causes a structural transition, leading to a new, crystalline compound, containing two interpenetrated networks. The state of the framework before transition (op vs. cp) influences the transition temperature: the small particles of the op phase transform at significantly lower temperature in comparison to the macroparticles of the cp phase, transforming close to the decomposition temperature. The new compound, confined closed pore phase (ccp), was characterized by powder X-ray diffraction and spectroscopic techniques, such as IR, EXAFS, and positron annihilation lifetime spectroscopy (PALS). Thermal effects of structural transitions were studied using differential scanning calorimetry (DSC), showing an overall exothermic effect of the process, involving bond breaking and reformation. Theoretical calculations reveal the energetics, driving the observed temperature induced phase transition.

14.
BMC Public Health ; 22(1): 1519, 2022 08 10.
Artículo en Inglés | MEDLINE | ID: mdl-35945518

RESUMEN

INTRODUCTION: Transport-related physical activity (TRPA) has been identified as a way to increase physical activity due to its discretionary and habitual nature. Factors thought to influence TRPA span multiple disciplines and are rarely systematically considered in unison. This systematic review aimed to identify cross-sectional and longitudinal factors associated with adult TRPA across multiple research disciplines. METHODS: Using four electronic databases, a systematic search of English, peer-reviewed literature from 2010 - 2020 was performed. Studies quantitatively examining factors associated with the outcome of adult TRPA were eligible. RESULTS: Seventy-three studies (n = 66 cross-sectional; n = 7 longitudinal) were included, cumulatively reporting data from 1,278,632 observations. Thirty-six factors were examined for potential association with TRPA and presented in a social-ecological framework: individual (n = 15), social (n = 3), and environmental (n = 18). Seven factors were found to be consistently associated with higher adult TRPA: lower socio-economic status, higher self-efficacy, higher social normalization, lower distance of travel, higher destination concentration, more streetlighting, and higher public transportation frequency with a greater number of terminals near route start and endpoints. CONCLUSIONS: This is the first comprehensive compilation of the correlates and determinants of adult TRPA. Seven individual, social, and environmental factors demonstrated consistent associations with TRPA. Models formed using these factors may facilitate more effective promotion of TRPA. There is a lack of longitudinal studies as well as studies assessing cognitive/attitudinal and social factors, highlighting gaps for further research. Those developing policies and strategies targeting TRPA need to consider a range of factors at the individual, social, and environmental level to maximise the likelihood of effectiveness.


Asunto(s)
Ejercicio Físico , Medio Social , Adulto , Estudios Transversales , Humanos , Autoeficacia , Transportes
15.
Angew Chem Int Ed Engl ; 61(39): e202210476, 2022 Sep 26.
Artículo en Inglés | MEDLINE | ID: mdl-35922393

RESUMEN

Self-assembly makes metallo-interlocked architectures attractive targets, but being in equilibrium with smaller species means that they can suffer from dilution effects. We show that a junctioned system gives rise to a [Pd4 (L)2 ]8+ trefoil entangled tetrahedron irrespective of concentration. Heating the sample reversibly shifts the equilibrium from the knot to an isomeric non-interlocked dual metallo-cycle, demonstrating that thermodynamic equilibria can still be exploited for switching even in the absence of concentration effects.

16.
J Am Chem Soc ; 143(11): 4143-4147, 2021 03 24.
Artículo en Inglés | MEDLINE | ID: mdl-33719416

RESUMEN

New nanoporous materials have the ability to revolutionize adsorption and separation processes. In particular, materials with adaptive cavities have high selectivity and may display previously undiscovered phenomena, such as negative gas adsorption (NGA), in which gas is released from the framework upon an increase in pressure. Although the thermodynamic driving force behind this and many other counterintuitive adsorption phenomena have been thoroughly investigated in recent years, several experimental observations remain difficult to explain. This necessitates a comprehensive analysis of gas adsorption akin to the conformational free energy landscapes used to understand the function of proteins. We have constructed the complete thermodynamic landscape of methane adsorption on DUT-49. Traversing this complex landscape reproduces the experimentally observed structural transitions, temperature dependence, and the hysteresis between adsorption and desorption. The complete thermodynamic description presented here provides unparalleled insight into adsorption and provides a framework to understand other adsorbents that challenge our preconceptions.

17.
Chemistry ; 27(37): 9708-9715, 2021 Jul 02.
Artículo en Inglés | MEDLINE | ID: mdl-33871114

RESUMEN

The switching mechanism of the flexible framework Zn4 O(benztb)1.5 (benztb=N,N,N',N'-benzidine tetrabenzoate), also known as DUT-13, was studied by advanced powder X-ray diffraction (PXRD) and gas physisorption techniques. In situ synchrotron PXRD experiments upon physisorption of nitrogen (77 K) and n-butane (273 K) shed light on the hitherto unnoticed guest-induced breathing in the MOF. The mechanism of contraction is based on the conformationally labile benztb ligand and accompanied by a reduction in specific pore volume from 2.03 cm3 g-1 in the open-pore phase to 0.91 cm3 g-1 in the contracted-pore phase. The high temperature limit for adsorption-induced contraction of 170 K, determined by systematic temperature variation of methane adsorption isotherms, indicates that the DUT-13 framework is softer than other mesoporous MOFs like DUT-49 and does not support the formation of overloaded metastable states required for negative gas-adsorption transitions.

18.
Langmuir ; 37(14): 4222-4226, 2021 04 13.
Artículo en Inglés | MEDLINE | ID: mdl-33797923

RESUMEN

New advanced adsorbents are a crucial driver for the development of energy and environmental applications. Tremendous potential is provided by machine learning and data mining techniques, as these approaches can identify the most appropriate adsorbent for a particular application. However, the current scientific reporting of adsorption isotherms in graphs and figures is not adequate to reproduce original experimentally measured data. This report proposes the specification of a new standard adsorption information file (AIF) inspired by the ubiquitous crystallographic information file (CIF) and based on the self-defining text archive and retrieval (STAR) procedure, also used to represent biological nuclear magnetic resonance experiments (NMR-STAR). The AIF is a flexible and easily extended free-format archive file that is readily human and machine readable and is simple to edit using a basic text editor or parse for database curation. This format represents the first steps toward an open adsorption data format as a basis for a decentralized adsorption data library. An open format facilitates the electronic transmission of adsorption data between laboratories, journals, and larger databases, which is key in the effort to increase open science in the field of porous materials in the future.

19.
Faraday Discuss ; 225: 286-300, 2021 02 01.
Artículo en Inglés | MEDLINE | ID: mdl-33136105

RESUMEN

Molecules in gas and liquid states, as well as in solution, exhibit significant and random Brownian motion. Molecules in the solid-state, although strongly immobilized, can still exhibit significant intramolecular dynamics. However, in most framework materials, these intramolecular dynamics are driven by temperature, and therefore are neither controlled nor spatially or temporarily aligned. In recent years, several examples of molecular machines that allow for a stimuli-responsive control of dynamical motion, such as rotation, have been reported. In this contribution, we investigate the local and global properties of a Lennard-Jones (LJ) fluid surrounding a molecular motor and consider the influence of cooperative and non-directional rotation for a molecular motor-containing pore system. This study uses classical molecular dynamics simulations to describe a minimal model, which was developed to resemble known molecular motors. The properties of an LJ liquid surrounding an isolated molecular motor remain mostly unaffected by the introduced rotation. We then considered an arrangement of motors within a one-dimensional pore. Changes in diffusivity for pore sizes approaching the length of the rotor were observed, resulting from rotation of the motors. We also considered the influence of cooperative motor directionality on the directional transport properties of this confined fluid. Importantly, we discovered that specific unidirectional rotation of altitudinal motors can produce directed diffusion. This study provides an essential insight into molecular machine-containing frameworks, highlighting the specific structural arrangements that can produce directional mass transport.

20.
Faraday Discuss ; 225(0): 84-99, 2021 02 04.
Artículo en Inglés | MEDLINE | ID: mdl-33104138

RESUMEN

Obtaining structural information for highly reactive metal-based species can provide valuable insight into important chemical transformations or catalytic processes. Trapping these metal-based species within the cavities of porous crystalline hosts, such as metal-organic frameworks (MOFs), can stabilise them, allowing detailed structural elucidation by single crystal X-ray diffraction. Previously, we have used a bespoke flexible MOF, [Mn3L2L'] (MnMOF-1, where L = bis-(4-carboxyphenyl-3,5-dimethylpyrazolyl)methane and L = L', but L' has a vacant N,N'-chelation site), which has a chelating site capable of post-synthetically binding metal ions, to study organometallic transformations and fundamental isomerisation processes. This manuscript will report the underlying conformational flexibility of the framework, demonstrate the solvent dependency of post-synthetic metalation, and show that the structural flexibility of the linker site and framework are critical to controlling and achieving high levels of metal loading (and therefore site occupancy) during chemical transformations. From these results, a set of design principles for linker-based "matrix isolation" and structure determination in MOFs are derived.

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