Wendy Lee Queen

Porous single-layer graphene (PG) offers an ideal platform for molecular-sieving membranes due to its atomically thin inorganic lattice and its ability to incorporate molecularly selective pores. However, the use of PG for high-temperature gas separation remains limited by the lack of a mechanically reinforcing film (MRF) that enables crack-free transfer onto porous supports and stable operation under pressurization. Here, we introduce a fluorinated porous organic polymer (FPOP) that provides the mechanical and thermal robustness needed to operate PG membranes at high temperature. The FPOP layer is deposited directly on PG from a molecular precursor solution. Upon drying and thermal annealing, it develops into a continuous cross-linked film that conforms to PG, maintains strong adhesion, and helps to avoid crack formation during the transfer of PG to a macroporous support. The FPOP film exhibits a quasi-ordered structure, forms an interface with graphene, and remains stable under pressurized conditions up to 350 °C. FPOP-supported PG membranes exhibit selective gas transport at elevated temperature (350 °C) and maintain their performance during extended mixed-gas operation. The membranes retain selective transport after humid/oxidative exposure and ambient storage. Importantly, the porous FPOP can regulate transport through enlarged nonselective graphene defects, thereby improving the selectivity of PG membranes. Overall, we demonstrate FPOP as a thermally stable MRF platform that enables crack-free PG transfer, high-temperature operation, and regulation of nonselective transport pathways.

Medical oxygen concentrators (MOCs) rely almost exclusively on lithium-exchanged zeolites for nitrogen-selective air separation, while growing lithium demand from battery manufacturing creates potential supply-chain vulnerabilities. This dependence motivates the exploration of alternative adsorbent classes. Metal–organic frameworks (MOFs) offer a structurally diverse alternative, yet no MOF has previously been evaluated at the process level for medical oxygen production. This work presents the first vacuum pressure swing adsorption (VPSA) process evaluation of a MOF adsorbent -Cr-BTC (MIL-100(Cr))- for medical oxygen concentration. Cr-BTC is among the few known MOFs to preferentially adsorb N2 over O2, owing to its coordinatively unsaturated Cr3+ sites. The material was synthesised (BET surface area: 2166 m2 g-1), and N2/ O2 isotherms were measured at 293–313 K; the intermediate curvature of the N2 isotherm motivated VPSA over conventional PSA. A two-bed VPSA modelling framework comprising adsorption, blowdown, purge, and pressurisation was developed in Aspen Adsorption and validated against experimental purity and product-flow data from a modified commercial LiLSX-based 10 LPM concentrator before being applied to Cr-BTC. A one-at-a-time parametric analysis identified a favourable operating condition: blowdown pressure PL = 0.8 bar, adsorption pressure PH = 2.0 bar, total cycle time tc = 12 s, with step times of 2.0 s for adsorption/purge and 4.0 s for blowdown/pressurisation. A structured grid sweep of 126 conditions found that 95 satisfied the WHO minimum purity threshold of 82%. Performance trade-off analysis shows simulated O2 purities up to 96% and recoveries up to 28.8%, while 5 of the 7 non-dominated points have specific energy consumptions at or below 1.0 kWh kg-1 O2, consistent with the WHO guideline value.

Defect engineering in Zr-based metal–organic frameworks (Zr-MOFs) has focused primarily on missing-linker defects. However, recent studies suggest that node dehydroxylation–which creates distortions and coordinatively unsaturated Zr sites (Zrcus)–may have a more significant impact on properties. The present work uses pair distribution function (PDF) and thermogravimetric analysis coupled with systematic defect manipulation to study the effect of node dehydroxylation and missing-linker defects in UiO-66. By employing rapid heat treatment (RHT) under humid flow, we tracked the transition from high-symmetry [Zr6O4(OH)4]12+ to distorted [Zr6O6]12+ nodes. This structural evolution significantly improves As(V) uptake, whereas increasing the number of missing linkers–via chemical treatment or RHT of mixed-ligand frameworks–fails to enhance performance. Crucially, our detection of distorted nodes in as-synthesized UiO-66 also raises the possibility that these defects were silently present in many earlier studies that span various applications, where their role in governing performance may have been inadvertently overlooked. The present study challenges the prevailing “missing-linker” paradigm and establishes cluster dehydroxylation as a defect-engineering strategy to enhance Lewis-acidic performance in Zr-MOFs.

Defect engineering in Zr-based metal-organic frameworks (Zr-MOFs) has focused primarily on missing-linker defects. However, recent studies suggest that node dehydroxylation–which creates distortions and coordinatively unsaturated Zr sites (Zr _cus )–may have a more significant impact on properties. The present work uses pair distribution function (PDF) analysis and systematic defect manipulation to decouple node dehydroxylation from missing-linker defects in UiO-66. By employing rapid heat treatment (RHT) under humid flow, we tracked the transition from high-symmetry [Zr6O4(OH)4] ¹²⁺ to distorted [Zr6O6] ¹²⁺ nodes. This structural evolution significantly improves As(V) uptake, whereas increasing the number of missing linkers–via chemical treatment or RHT of mixed-ligand frameworks–fails to enhance performance. Crucially, our detection of distorted nodes in as-synthesized UiO-66 also raises the possibility that these defects were silently present in many earlier studies that span various applications, where their role in governing performance may have been inadvertently overlooked. The present study challenges the prevailing ”missing-linker” paradigm and establishes cluster dehydroxylation as a defect-engineering strategy to enhance Lewis-acidic performance in Zr-MOFs.

Metal‐organic frameworks (MOFs) featuring high densities of selective metal binding sites represent promising materials for the extraction of toxic metal ions from liquids. This study presents a Zr‐MOF containing accessible thiol functionalities that demonstrates exceptional adsorption capacity and recyclability for the capture of lead(II) ions (Pb(II)). Structural characterization via Pair Distribution Function (PDF) and Powder X‐ray diffraction (PXRD) analyses revealed well‐defined Zr‐clusters interconnected via meso‐2,3‐dimercaptosuccinic acid (DMSA) linkers. The framework exhibits limited long‐range structural order and high ligand flexibility that facilitates Pb(II) chelation. Sequential adsorption/desorption cycles monitored via X‐ray Photoelectron Spectroscopy (XPS), solid‐state NMR, and PDF established that: (i) strong chelation occurs between Pb(II) and DMSA through both thiol and carboxylate functionalities and (ii) this chelation is reversible under acidic conditions, enabling complete adsorbent regeneration. Beyond its high performance in lead removal from water, the practical utility of Zr‐DMSA was further demonstrated through the removal of Pb(II) from damaged Pb‐based perovskite solar cells, with efficacy confirmed at both ambient and elevated temperatures. These results highlight the potential of thiol‐bearing Zr‐MOFs as efficient, cyclable adsorbents for heavy metal remediation applications.

This paper explores the development and testing of a simple absorption correction model for processing powder X-ray diffraction data from Debye–Scherrer geometry laboratory X-ray experiments. This may be used as a preprocessing step before using PDFgetX3 to obtain reliable pair distribution functions (PDFs). Various experimental and theoretical methods for estimating μR were explored, and the most appropriate μR values for correction were identified for different capillary diameters and X-ray beam sizes. We identify operational ranges of μR where a reasonable signal-to-noise ratio is possible after correction. A user-friendly software package, diffpy.labpdfproc, is presented that can help estimate μR and perform absorption corrections with a rapid calculation for efficient processing.

A sustainable clay-to-zeolite synthesis cuts CO ₂ emissions by 90%, enabling high-performance CO ₂ /H ₂ O adsorption with minimal environmental impact.