Variable Temperature Powder X-ray Diffraction Research Articles

The Changing Phases of Bromopentafluorobenzene.

As part of a much larger study on non-covalent interactions in binary adducts, we have explored the solid-state structures of bromopentafluorobenzene (C6F5Br) using differential scanning calorimetry (DSC), variable-temperature powder X-ray diffraction (VT-PXRD), and single-crystal X-ray diffraction (SXD). DSC data initially indicated a single solid-state phase below the freezing point, but revealed additional weak transitions upon heating. The crystal structures of three solid-state phases have been solved. The SXD data showed that phases I and IV are centrosymmetric, whilst phase II is polar. However, the structure of phase III remains elusive due to the changing phase behaviour of C6F5Br that is determined as much as by kinetics as thermodynamics. The results underline the need for multiple analytical techniques to study non-covalent interactions and offer valuable data for refining computational models in crystal structure prediction and machine learning. A comparison with the iodinated counterpart is also made.

Anion-intercalation pseudocapacitance in oxygen vacancy-rich spinel-perovskite NiFe2O4-LaFeO3 nanocomposite for high energy density asymmetric supercapacitor application

Oxide nanomaterials have attracted significant attention as energy storage materials. The combination of spinel-perovskite oxides as nanocomposites creates dense oxygen vacancies (VO) at the hetero-interface. VO present in the complex oxides are indispensable for energy conversion applications. Herein, we demonstrated the one pot synthesis of spinel-perovskite NiFe2O4-xLaFeO3 nanocomposite and investigated the phase formation using variable temperature powder X-ray diffraction of the gel precursor. The role of oxygen-vacancy mediated tuneable redox transitions in NiFe2O4-xLaFeO3 nanocomposite has been understood. The anion-intercalation-based pseudocapacitance and the oxygen intercalation have been exploited for high-performance electrochemical energy storage. The NiFe2O4–2LaFeO3 exhibited a high specific capacity of 652 C g−1 at a current density of 2 A g−1. The fabricated NiFe2O4–2LaFeO3||NiCo2O4 asymmetric supercapacitor device (ASC) exhibited excellent cyclability over 20,000 cycles with superior capacity retention and high Coulombic efficiency (92 %) and achieved a high energy density of 42.5 Wh kg−1 at a power density of 1500 W kg−1. The presence of VO and the mixed-valence states of Fe2+/3+ were confirmed by XPS-depth profiling. The tuneable redox transition of Fe2+/3+ and VO contribute to the higher pseudocapacitance response.

Luminescence modulated by molecular conformation in stimuli-responsive polymorphs of dibenzothiaborinine dioxide-pyridylphenolate complex

Novel spirane organoboron complex, SO2-pp, composed of highly electron-accepting dibenzo[b,e][1,4]thiaborinine 5,5-dioxide scaffold and 2-(2-pyridyl)phenolate ligand exhibits moderate-to-strong fluorescence in solution and solid state. Photophysical properties of this system strongly depend on the conformation of the molecule. Specifically, due to the semi-labile nature of organoboron moiety as well as the asymmetric character of the ligand, two distinctive conformations can be distinguished. Their occurrence in the solid state is regulated by the crystallization conditions leading to the formation of two polymorphic phases exhibiting sky blue (SO2-pp-α, λ = 446 nm, ΦF = 70 %) and green (SO2-pp-β, λ = 489 nm, ΦF = 36 %) emission, respectively. Their crystal structures, stability and photophysical properties were comprehensively studied by DSC, single-crystal XRD and variable-temperature PXRD. Periodic DFT calculations showed that the lattice energy of SO2-pp-β polymorph is by 28 kJ‧mol−1 more favoured (7 kJ‧mol−1 per molecule, optimization in periodic boundary conditions) owing to more efficient intermolecular interactions in the crystal structure. In contrast, the molecule of the kinetic SO2-pp-α phase adopts more stable conformation (energy difference of 4.7 kJ‧mol−1, single-molecule DFT optimization) which can be ascribed to the formation of intramolecular C–H⋯O hydrogen bond interaction. Both forms show sensitive tricolor reversible response under mechanical and temperature stimuli. Under grinding, they gradually turn into cyan (λ = 479 nm) amorphous phase (SO2-pp-A). This process can be reversed by heating or exposure to CHCl3 vapours.

The further development of the borate nitrate family: Synthesis and characterization of Ag12(B9O18)(NO3)3 with unique isolated B9O18 clusters, 9B:6Δ3□:3(–)

Single crystals of a novel silver borate nitrate, Ag12(B9O18)(NO3)3 (1), were produced as a byproduct upon preparation of Ag3B6O10(NO3). 1 is hexagonal, (P63/m, a = 11.2896(3) Å, c = 11.6693(3) Å); its structure exhibits just a second example of unique [B9O18]9– nonaborate anions [9B:6Δ3□:3(<2Δ□>–)<3□>] which can be described as three triborate groups linked in a large cycle. As commonly observed among silver borates, the Ag+ cations exhibit strongly anharmonic vibrations which were described using Gram–Chariler series up to 4th order. 1 is characterized by single-crystal X-ray diffraction, variable-temperature powder X-ray diffraction, IR, Raman, and UV–vis-NIR spectroscopy, complex thermal analysis, and DFT calculations. The thermal expansion of 1 is slightly anisotropic (αa = 15.0, αc = 17.7 × 10−6 °C−1 at 200 °C). Upon heating, the compound decomposes with formation of metallic silver and another borate, AgBO2, which could be earlier prepared only at high oxygen pressure.

The Halogenation Effect Induces a Variety of Switchable Phase Transition and Second-Harmonic-Generation Materials.

Halogen engineering offers a means of enhancing the physical properties of materials by fine-tuning the rotational energy barrier and dipole moment, which proved to be effective in achieving switchable phase transitions and optical responses in materials. In this work, by substituting the methyl group in ligand N-ethyl-1,5-diazabicyclo[3.3.0]octane (CH3CH2-3.3.0-Dabco) with halogen atoms X (Cl or Br) and then contining to react it with FeBr3 in a HBr aqueous solution, we successfully synthesized three kinds of organic-inorganic hybrid switchable phase-change materials, [CH3CH2-3.3.0-Dabco]FeBr4 (1), [ClCH2-3.3.0-Dabco]FeBr4 (2), and [BrCH2-3.3.0-Dabco]FeBr4 (3), which were fully characterized by single-crystal X-ray diffraction and variable-temperature powder X-ray diffraction. Compared to compound 1, compounds 2 and 3 show two pairs of reversible phase transitions, dielectric anomalies, and a second-harmonic-generation effect, which are successfully induced due to the halogen substitution. This study offers an effective molecular design strategy for the exploration and construction of iron halide organic-inorganic hybrid materials with temperature-adjustable physical properties.

Host-Host Interactions Enhanced the Structural Rigidity in a 6-Fold Interpenetrated Diamondoid Metal-Organic Framework Exhibiting C2H2/C2H4 Separation.

Multi-interpenetrated metal-organic frameworks (MOFs) have exhibited excellent performance in selective adsorption due to the variable post-interspersed flexibility, but the design and control remain challenging. Herein, two anthracene-based ligands, 4,4'-(anthracene-9,10-diyl)dibenzoic acid (H2L1) and 9,10-di(pyridin-4-yl)anthracene (L2), are used to construct a new three-dimensional 6-fold interpenetrated MOF [Zn(L1)(L2)]n (NBU-X1), which exhibits multiple C-H···π interactions that enhance the structural rigidity, thereby entangling with a C2H2/C2H4 separation performance. In this material, the incorporation of abundant anthracene rings within the framework not only partitions and restricts the pore window size to a quasi-double pore but also stabilizes it through host-host interactions. The structural stability upon heating or guest displacement/removal has been investigated by single-crystal X-ray diffraction and in situ variable-temperature powder X-ray diffraction, in contrast to the extreme flexibility of most multi-interpenetrated MOFs. The performance of purifying C2H4 from C2H2/C2H4 mixtures has been proved by dynamic breakthrough tests.

Transition from isotropic positive to negative thermal expansion by local Zr6O8 node distortion in MOF-801

The chemical designability and diversity of metal-organic frameworks (MOFs) endow them with plenty of anomalous properties, such as negative thermal expansion (NTE). Herein, we investigated the thermal expansion behaviors of the well-known MOF-801, which has been widely used in water adsorption and gas separation. The analyses of variable temperature powder X-ray diffraction and Rietveld refinements revealed a fascinating transition from positive thermal expansion to NTE. Further in situ Raman spectra and pair distribution function investigations shed light on the transition being attributed to the local Zr6O8 node distortion rather than a long-range phase transition. Our findings will enhance the comprehension of NTE and contribute to the effective utilization of MOF-801 over a broad temperature range.

Thermoanalytical techniques applied to the solid-state characterization of atorvastatin calcium trihydrate form I

Atorvastatin calcium trihydrate (ACT) is a synthetic lipid-lowering agent whose thermal character remains largely unknown or else mischaracterized due to being called both “atorvastatin” and “atorvastatin form I” indiscriminately in the literature. Developing stable drugs, however, requires ensuring and thus understanding the reliable thermal behavior of trihydrate drugs, for pharmaceutical manufacturing can involve temperatures that might cause phase transition and/or the dehydration of the drugs, with implications for its physical characteristics, its chemical characteristics, and/or the pharmaceutical product's bioactivity. Against that background, in our study we investigated both a solid-state and thermal characterization of ACT via powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), hot-stage microscopy (HSM), and ex situ variable temperature PXRD techniques, all as integral parts of drug development. DSC and TGA curves clarified ACT's thermal stability and dehydration, and the ACT sample was identified as Form I of the trihydrate, which remains stable until approximately 40 °C. DSC showed no significant changes during melting with different heating rates, while the TGA curve revealed the stepwise loss of water molecules following heating. Ex situ PXRD suggested no abrupt changes to the trihydrate's crystal lattice during the dehydration of the first two moles of water molecules. Moreover, HSM clearly showed a unique water loss event never before visualized. Last, HSM confirmed the drug's crystallinity, its crystal shape, and the presence of an isotropic liquid after continuous heating, which remained until cooling to room temperature.

Combining a Drug and a Nutraceutical: A New Cocrystal of Praziquantel and Curcumin

This study explores the co-crystallization between the drug praziquantel (PZQ) and the nutraceutical curcumin (CU). The investigation revealed two novel solid forms: a cocrystal solvate with ethyl acetate and a non-solvated cocrystal. This novel drug–nutraceutical cocrystal is a praziquantel–curcumin (2:1) cocrystal. The cocrystal solvate has ethyl acetate molecules occupying the voids with minimal interactions within the crystal lattice. The application of heat treatment induces solvent removal and prompts the transition to the non-solvated cocrystal, as highlighted by variable-temperature X-ray powder diffraction (VT-XRPD). Thermal analyses demonstrate the stability of the cocrystal solvate up to approximately 100 °C, beyond which it transforms into the non-solvated phase, which eventually melts at 130 °C.

Systematic study of ionic conduction in silver iodide/mesoporous alumina composites 2: effects of silver bromide doping.

In our preceding paper (Y. Fukui et al., Phys. Chem. Chem. Phys., 2023, 25, 25594-25602), we reported a systematic study of the Ag+-ion conducting behaviour of silver iodide (AgI)-loaded mesoporous aluminas (MPAs) with different pore diameters and AgI-loading ratios. By optimising the control parameters, the Ag+-ion conductivity has reached 7.2 × 10-4 S cm-1 at room temperature, which is more than three orders of magnitude higher than that of bulk AgI. In the present study, the effect of silver bromide (AgBr)-doping in the AgI/MPA composites on Ag+-ion conductivity is systematically investigated for the first time, using variable-temperature powder X-ray diffraction, differential scanning calorimetry, and electrochemical impedance spectroscopy measurements. The AgBr-doped AgI/MPA composites, AgI-AgBr/MPA, formed a homogeneous β/γ-AgI-structured solid solution (β/γ-AgIss) for the composites with AgBr ≤ 10 mol%, above which the composites underwent a phase separation into β/γ-AgIss and face-centred cubic AgBr solid solutions (AgBrss). The onset temperature of the exothermic peaks attributed to the transition from α-AgI-structured solid-solution phase to β/γ-AgIss or AgBrss decreased with increasing the AgBr-doping ratio. The room-temperature ionic conductivity of the AgI-AgBr/MPA composites exhibited a volcano-type dependence on the AgBr-doping ratio with the highest value (1.6 × 10-3 S cm-1) when the AgBr content was 10 mol%. This value is more than twice as high as that of the highest conducting AgI/MPA found in our previous study.

Artificial vitriols: a contemporary interpretation of historical ingredients.

"Vitriol" is a term that appeared during the Middle-Ages to indicate a wide range of ingredients widely used both in medicinal and alchemical recipes. Green, blue, or white vitriols are easily associated with iron(ii), copper(ii), and zinc sulphate respectively thanks to the historical sources composed in the time period when the ancient and modern nomenclatures overlapped. However, other colours of vitriols are attested throughout history, such as yellow, red, or black. The identification of these compounds is significantly less straightforward, and often chalked up to Decknamen (code names) or unspecified impure ores. Moreover, from several sources it is apparent that some of these compounds are artificial, or at least the result of technical operations rather than mineral ores used as they are. By thermal manipulation of iron(ii) sulphate, we managed to identify several compounds that fit with historical descriptions, which were later characterized through XRPD. Moreover, by using a Kofler bench and variable temperature XRPD, we were able to further investigate the transitions between these phases.

Loading and thermal behaviour of ZIF-8 metal-organic framework-inorganic glass composites.

Here we describe the synthesis of a compositional series of metal-organic framework crystalline-inorganic glass composites (MOF-CIGCs) containing ZIF-8 and an inorganic phosphate glass, 20Na2O-10NaCl-70P2O5, to expand the library of host matrices for metal-organic frameworks. By careful selection of the inorganic glass component, a relatively high loading of ZIF-8 (70 wt%) was achieved, which is the active component of the composite. A Zn⋯O-P interfacial bond, previously identified in similar composites/hybrid blends, was suggested by analysis of the total scattering pair distribution function data. Additionally, CO2 and N2 sorption and variable-temperature PXRD experiments were performed to assess the composites' properties.

Highly Selective p-Xylene Separation from Mixtures of C8 Aromatics by a Nonporous Molecular Apohost.

High and increasing production of separation of C8 aromatic isomers demands the development of purification methods that are efficient, scalable, and inexpensive, especially for p-xylene, PX, the largest volume C8 commodity. Herein, we report that 4-(1H-1,2,4-triazol-1-yl)-phenyl-1H-benzo[de]isoquinoline-1,3(2H)-dione (TPBD), a molecular compound that can be prepared and scaled up via solid-state synthesis, exhibits exceptional PX selectivity over each of the other C8 isomers, o-xylene (OX), m-xylene (MX), and ethylbenzene (EB). The apohost or α form of TPBD was found to exhibit conformational polymorphism in the solid state enabled by rotation of its triazole and benzene rings. TPBD-αI and TPBD-αII are nonporous polymorphs that transformed to the same PX inclusion compound, TPBD-PX, upon contact with liquid PX. TPBD enabled highly selective capture of PX, as established by competitive slurry experiments involving various molar ratios in binary, ternary, and quaternary mixtures of C8 aromatics. Binary selectivity values for PX as determined by 1H NMR spectroscopy and gas chromatography ranged from 22.4 to 108.4, setting new benchmarks for both PX/MX (70.3) and PX/EB (59.9) selectivity as well as close to benchmark selectivity for PX/OX (108.4). To our knowledge, TPBD is the first material of any class to exhibit such high across-the-board PX selectivity from quaternary mixtures of C8 aromatics under ambient conditions. Crystallographic and computational studies provide structural insight into the PX binding site in TPBD-PX, whereas thermal stability and capture kinetics were determined by variable-temperature powder X-ray diffraction and slurry tests, respectively. That TPBD offers benchmark PX selectivity and facile recyclability makes it a prototypal molecular compound for PX purification or capture under ambient conditions.

Stable and rapid thermochromic reversibility in acene alkylamine intercalated layered hybrid perovskites

Since the discovery of thermochromism in halide perovskites, new perovskite materials with excellent thermochromic properties have been developed. Among them, two-dimensional (2D) layered hybrid perovskites have been extensively explored because of their highly tunable structures and unique thermochromic responses. In this study, the thermochromism in acene alkylamine-spaced 2D perovskite single crystals (PEA)2PbI4 and (NEA)2PbI4 (PEA = 2-phenylethylammonium, NEA = 2-(2-naphthyl)-ethanammonium) is studied. These 2D perovskites undergo a distinct color change between orange and red during heating and cooling cycles, with the corresponding optical bandgap modulation monitored by variable-temperature absorption spectroscopy. The thermochromism in (PEA)2PbI4 and (NEA)2PbI4 is caused by lattice expansion, as confirmed by thermogravimetric–differential scanning calorimetry and variable-temperature powder X-ray diffraction. Compared with the thermochromism caused by structural phase transition, lattice-expansion-modulated thermochromism demonstrates rapid color change and luminescence recovery, and enhanced thermal cycling stability. This study presents a new strategy for developing thermochromic halide perovskites for multifunctional applications.

Structure and dielectric properties in Mg/Nb co-substituted bismuth sodium titanate

A systematic study of pseudo-isovalent B site co-substitution of Ti4+ by Mg2+ and Nb5+ in bismuth sodium titanate is presented. A complete solid solution in the Bi0.5Na0.5Ti1−x(Mg1/3Nb2/3)xO3 system is formed. With increasing level of substitution, dielectric anomalies associated with depoling and maximum permittivity temperatures (Td and Tm, respectively) are suppressed and shift to lower temperatures. Variable temperature X-ray powder diffraction on the x = 0.2 composition reveals a non-linear thermal expansion at temperatures below Tm. B-site co-substitution by Mg and Nb has the effect of interrupting the long-range ferroelectric ordering in the system, resulting in lower saturation and remnant polarizations. A maximum energy storage density of 4.14 J cm−3 with a recoverable energy density of 2.35 J cm−3 was obtained for the x = 0.1 composition, while the x = 0.5 composition appears to have the best balance between energy storage and energy efficiency.

A novel contribution to the M3B6O10X hexaborate family: The new silver compound Ag3B6O10Br and thermal behavior of Ag3B6O10(NO3) and Na3B6O10I

In this work, we present a new borate, Ag3B6O10Br, as well as thermal properties of two recently reported members of M3B6O10X family, Ag3B6O10(NO3) and Na3B6O10I. The structure of Ag3B6O10Br is non-centrosymmetric, Pnm21, and exhibits a new version of packing the ionic Ag–Br and covalent B–O frameworks. The non-centrosymmetry is induced by alternation of disordered and ordered borate “layers” normal to a. The Ag–Br sublattice is also strongly disordered and exhibits pronounced ahnarmonicity of thermal vibrations modeled using the Gram – Charlier series. Thermal behavior of Ag3B6O10Br, Ag3B6O10(NO3) and Na3B6O10I was characterized using variable-temperature powder X-ray diffraction and thermal analysis. The thermal behavior of Ag3B6O10Br (αa = −0.5, αb = −7.4, αc = 41.5 at 200°С), Ag3B6O10(NO3) (αa = 4.5, αb = 4.8, αc = 31.8 at 200°С), and Na3B6O10I (αa = 9.4, αb = −1.2, αc = 48.3 at 200°С) is strongly anisotropic due to the alignment of the hexaborate B6O13 groups in the structure.

Hydrogen-bonded nickel(II)-organosulfonate framework: Thermal expansion behavior, proton conduction, and magnetic properties

Metalo Hydrogen-bonded organic frameworks are emerging supramolecular platforms for designing functional molecular materials. Herein, we reported the supramolecular structure, thermal, magnetic, and proton conduction properties of a hydrogen-bonded nickel(II)-organosulfonate framework, [Ni(H2O)6][NPS]2 (NiHOF, HNPS = naphthalene-2-sulphonic acid). Single-crystal X-ray diffraction studies reveal a two-dimensional hydrogen-bonded network sustained by multiple and charge-assisted OH···O H bonds between hexaaquanickel(II) cations and organosulfonate anions. Additionally, continuous ca. 0.47 × 0.70 nm2 windows were formed within the framework. The thermal stability of the NiHOF was confirmed by thermal gravimetric analysis and variable temperature single-crystal and powder X-ray diffraction patterns. N2 sorption isotherms suggest an ultramicroporous supramolecular framework of NiHOF with permanent porosity. The anisotropic positive thermal expansion behavior of NiHOF was evidenced by the dynamic crystallography experiments. Magnetic measurements indicate easy-axis magnetic anisotropy (D = -10.5 cm−1) of the NiHOF while no slow magnetic relaxation behavior. Electrochemical impedance spectroscopy indicates the temperature and humidity dependence of conductivities of NiHOF. At 50 °C and 70% relative humidity, the conductivity is 1.13 × 10−4 S·cm−1, revealing a supramolecular proton conductor of NiHOF. This work provides a potential way for designing novel thermal, magnetic, and electrical molecular materials through the supramolecular assembly of inorganic and organosulfonate synthons.

Thermodynamic and Kinetic Mechanism of the Phase Transition from Aztreonam Dihydrate to Anhydrates

In this work, two anhydrates (form A and form B) and one dihydrate (form C) of aztreonam were found and were characterized by powder X-ray diffraction (PXRD), thermogravimetric analysis, differential thermal analysis, and Fourier transform infrared spectroscopy. Dynamic vapor adsorption and variable-temperature PXRD experiments were carried out to study their thermal stability and moisture absorption stability. Furthermore, the critical water activity of aztreonam at 10–45 °C was determined, and it was found that the water activity determines the dehydration process of form C. The solubility of form A and form B in methanol solvent was measured at 10–45 °C to decide the thermodynamic stability of the polymorphs, and it was found that form B is thermodynamically stable below 28 °C, while form A is thermodynamically stable above 28 °C. The competitive suspension experiments further proved that form A and form B are enantiotropic polymorphs. In addition, the solution-mediated phase transition (SMPT) process of aztreonam form C was in situ monitored using Raman spectroscopy. The results show that the SMPT process is jointly controlled by the dissolution of the dihydrate and the nucleation of anhydrates, in which temperature plays a very important role. Finally, the SMPT mechanism of the dihydrate form is proposed.

Metalo Hydrogen-Bonded Organic Frameworks Self-Assembled by Charge-Assisted Synthons for Ultrahigh Proton Conduction

Hydrogen-bonded organic frameworks (HOFs) have been well recognized for constructing solid-state proton-conducting materials due to their inherent well-defined H-bonded networks; however, the design and synthesis of stable HOFs showing ultrahigh superprotonic conductivity is still challenging. Herein, we reported a facile and effective synthetic strategy to build high proton-conducting metalo hydrogen-bonded organic–inorganic frameworks (MHOFs) through charge-assisted inorganic and organic synthons. The supramolecular self-assembly of simple metal salts and tetra-carboxylic acids gives rise to two hydrogen-bonded frameworks, [M(H2O)6][H2tcba] (M = Zn2+, Ni2+; H4tcba = 1,2,4,5-benzenetetracarboxylic acid). X-ray crystallography and gas adsorption confirmed the nonporous nature of the HOIFs. Variable-temperature single-crystal and powder X-ray diffraction experiments reveal the thermal and water stability of the supramolecular structures sustained by exclusively charge-assisted hydrogen bonds. The high density of carboxylic acid groups and coordinated water molecules provide ample protons and hydrophilic environments for efficient proton transport; therefore, variable-temperature and -humidity electrochemical impedance spectroscopy revealed that MHOFs are good supramolecular proton conductors with conductivities up to 1.1 × 10–2 and 2.1 × 10–2 S·cm–1 for 1 and 2, respectively, at 80 °C under 97% RH. Our study demonstrates great potential of charge-assisted inorganic and organic synthons in the design and construction of proton-conducting HOIFs.

Highly Productive C3H4/C3H6 Trace Separation by a Packing Polymorph of a Layered Hybrid Ultramicroporous Material.

Ultramicroporous materials can be highly effective at trace gas separations when they offer a high density of selective binding sites. Herein, we report that sql-NbOFFIVE-bpe-Cu, a new variant of a previously reported ultramicroporous square lattice, sql, topology material, sql-SIFSIX-bpe-Zn, can exist in two polymorphs. These polymorphs, sql-NbOFFIVE-bpe-Cu-AA (AA) and sql-NbOFFIVE-bpe-Cu-AB (AB), exhibit AAAA and ABAB packing of the sql layers, respectively. Whereas NbOFFIVE-bpe-Cu-AA (AA) is isostructural with sql-SIFSIX-bpe-Zn, each exhibiting intrinsic 1D channels, sql-NbOFFIVE-bpe-Cu-AB (AB) has two types of channels, the intrinsic channels and extrinsic channels between the sql networks. Gas and temperature induced transformations of the two polymorphs of sql-NbOFFIVE-bpe-Cu were investigated by pure gas sorption, single-crystal X-ray diffraction (SCXRD), variable temperature powder X-ray diffraction (VT-PXRD), and synchrotron PXRD. We observed that the extrinsic pore structure of AB resulted in properties with potential for selective C3H4/C3H6 separation. Subsequent dynamic gas breakthrough measurements revealed exceptional experimental C3H4/C3H6 selectivity (270) and a new benchmark for productivity (118 mmol g-1) of polymer grade C3H6 (purity >99.99%) from a 1:99 C3H4/C3H6 mixture. Structural analysis, gas sorption studies, and gas adsorption kinetics enabled us to determine that a binding "sweet spot" for C3H4 in the extrinsic pores is behind the benchmark separation performance. Density-functional theory (DFT) calculations and Canonical Monte Carlo (CMC) simulations provided further insight into the binding sites of C3H4 and C3H6 molecules within these two hybrid ultramicroporous materials, HUMs. These results highlight, to our knowledge for the first time, how pore engineering through the study of packing polymorphism in layered materials can dramatically change the separation performance of a physisorbent.