Adam J. Matzger

Metal‐free purely organic phosphors (POPs) are attractive triplet emitters, but their room‐temperature phosphorescence (RTP) is often slow at milliseconds or longer because the radiative T ₁ →S ₀ transition is spin‐forbidden. Here, we introduce directional carbonyl orientation (DCO) as a packing‐aware conformational descriptor for understanding and designing fast metal‐free RTP. In brominated terephthalate derivatives, co‐directional carbonyl torsions are associated with fast RTP, whereas counter‐directional torsions are associated with slower RTP. Using two polymorphs of dimethyl dibromoterephthalate (MeBrTPA), we show that the co‐directional Form I emits blue RTP with Φ _phos = 24%, τ _phos = 15 µs, and an estimated k _r = 1.6 × 10 ⁴ s ⁻¹ , while the counter‐directional Form II is slower despite its higher quantum yield. State‐resolved TD‐DFT/SOC calculations further reveal that the difference cannot be described by direct S ₀ –T ₁ coupling alone, but instead reflects distinct state‐specific combinations of T ₁ –S _n SOC and S _n –S ₀ transition strength. Finally, translating the DCO‐favored geometry from crystal packing into molecular design, conformational locking in CyclicBrTPA produces fast blue RTP in amorphous PMMA. Together, these results establish DCO as a practical molecular design strategy for organizing favorable spin‐coupling geometries beyond a single crystal‐packing environment, while highlighting the continued importance of a sufficiently rigid environment for room‐temperature emission.

Metal‐free purely organic phosphors (POPs) are attractive triplet emitters, but their room‐temperature phosphorescence (RTP) is often slow at milliseconds or longer because the radiative T ₁ →S ₀ transition is spin‐forbidden. Here, we introduce directional carbonyl orientation (DCO) as a packing‐aware conformational descriptor for understanding and designing fast metal‐free RTP. In brominated terephthalate derivatives, co‐directional carbonyl torsions are associated with fast RTP, whereas counter‐directional torsions are associated with slower RTP. Using two polymorphs of dimethyl dibromoterephthalate (MeBrTPA), we show that the co‐directional Form I emits blue RTP with Φ _phos = 24%, τ _phos = 15 µs, and an estimated k _r = 1.6 × 10 ⁴ s ⁻¹ , while the counter‐directional Form II is slower despite its higher quantum yield. State‐resolved TD‐DFT/SOC calculations further reveal that the difference cannot be described by direct S ₀ –T ₁ coupling alone, but instead reflects distinct state‐specific combinations of T ₁ –S _n SOC and S _n –S ₀ transition strength. Finally, translating the DCO‐favored geometry from crystal packing into molecular design, conformational locking in CyclicBrTPA produces fast blue RTP in amorphous PMMA. Together, these results establish DCO as a practical molecular design strategy for organizing favorable spin‐coupling geometries beyond a single crystal‐packing environment, while highlighting the continued importance of a sufficiently rigid environment for room‐temperature emission.

Although metal–organic frameworks (MOFs) provide molecular selectivity in separations, understanding diffusion within these materials remains challenging due to the intertwined contributions of inherent pore architecture and grain boundaries in packed‐bed systems. To isolate the intracrystalline diffusion behavior, molecular transport across MOF single crystals was investigated in binary and ternary liquid‐phase systems. Diffusion rates were found to vary significantly even among guest molecules with identical kinetic diameters. By isolating the intracrystalline diffusion process, the slow transport is attributed to strong guest–framework interactions rather than pore clogging. This is corroborated by the increase in diffusion rates upon reducing the guest–framework interactions through selection of a more strongly interacting solvent. This study provides mechanistic insights into intrinsic diffusion in MOFs and benchmark behavior to calibrate computational approaches.

Although metal–organic frameworks (MOFs) provide molecular selectivity in separations, understanding diffusion within these materials remains challenging due to the intertwined contributions of inherent pore architecture and grain boundaries in packed‐bed systems. To isolate the intracrystalline diffusion behavior, molecular transport across MOF single crystals was investigated in binary and ternary liquid‐phase systems. Diffusion rates were found to vary significantly even among guest molecules with identical kinetic diameters. By isolating the intracrystalline diffusion process, the slow transport is attributed to strong guest–framework interactions rather than pore clogging. This is corroborated by the increase in diffusion rates upon reducing the guest–framework interactions through selection of a more strongly interacting solvent. This study provides mechanistic insights into intrinsic diffusion in MOFs and benchmark behavior to calibrate computational approaches.

The necessity of solvent exchange and evacuation for metal–organic framework (MOF) activation is investigated using HKUST-1, UiO-66, and Zn-MOF-74 as model systems. High surface areas are achieved by simple thermal treatment directly from either the synthesis solvent or the activation solvent. The process requires careful control over time and temperature, as removal of guest solvent molecules competes with linker decomposition. Detailed studies on HKUST-1 reveal the liberation of benzene accompanying material decomposition. NMR spectroscopy data complement TGA-MS data to reveal stepwise linker decarboxylation and an autocatalytic decomposition mechanism. Material collapse, evidenced by a surface area decline upon extended thermal treatment, is found to be accelerated by certain residual solvents, albeit with a mechanism distinct from the commonly invoked mechanism of capillary force-induced collapse.

The final step in revealing the porosity of most metal‐organic frameworks (MOFs), the ultimate step of the activation process, involves removal of solvent from the pores. This is commonly accomplished with the application of vacuum and heat; whereas some MOFs are readily activated under mild conditions, others must be heated to the point where decomposition can compete with activation. This latter class includes MOFs where the coordination of the metals to solvent must be disrupted for full activation. Here, the details of the solvent removal process are elucidated for two isostructural MOFs comprising divalent metals linked with 2,5‐dioxidoterephthalate: Mg‐MOF‐74 and Zn‐MOF‐74. Using computational and spectroscopic data, structural and electronic changes undergone by the MOF are elucidated, providing insight into discrete intermediate states during the solvent removal process. Additionally, powder x‐ray diffraction is analyzed to reveal features that are indicative of successful activation. These results provide a basis to design more efficient and effective MOF activation procedures.

The unique properties of porous metal–organic frameworks (MOFs) make them amenable to simple estimation of their standard formation enthalpies(ΔHf◦) using a modification to Benson group increment theory (BGIT); this approach fills a void in the literature because extracting such data from first-principles calculations is generally not computationally feasible. The method is illustrated for MOFs based on both the basic Zn carboxylate and Cu paddlewheel secondary building units, with approaches outlined for further extension to additional MOF classes. Simple access to ΔHf◦(MOF) values informs stability relationships between dense and porous phases and is critical for applications involving energetic MOF composites.

Explosives underpin applications ranging from military technologies to mining and construction. Safety risks during material transport are often mitigated using formulation strategies, such as polymer bonding, that reduce sensitivity; however, reduced sensitivity can result in incomplete detonation, compromising performance. These competing demands motivate the development of switchable energetic materials whose sensitivity can be externally activated to enable truly on-demand detonation. We demonstrate that novel spiropyran compounds (1-SP and 2-SP), designed to function as electrostatic molecular switches, enable the modulation of explosive sensitivity using light as the sole external stimulus, forming a zwitterionic merocyanine (MC). Pure HMX crystals were shown to be less sensitive to impact than 5 wt % 1-SP and 1 wt % 2-SP coated crystals following UV irradiation, as the impact sensitivity, E50, decreased from 2.7 ± 0.1 J to 2.2 ± 0.1 J for 1-MC and 2.3 ± 0.1 J for 2-MC. Furthermore, these compounds are seamlessly integrated into the research formulation, PBXN-110. Impact sensitivity decreased to 3.8 ± 0.1 J for 1 wt % 1-SP and 4.7 ± 0.1 J for 1 wt % 2-SP, relative to pure HMX (2.7 ± 0.1 J) when encased within the PBXN-110. When exposed to UV light, the 1 wt % 1-MC material exhibits an E50 of 3.2 ± 0.1 J and 1 wt % 2-MC of 3.8 ± 0.1 J, demonstrating the ability of the merocyanine compounds to affect sensitivity even within a polymer matrix. Integration of these compounds into established desensitization strategies provides an unprecedented platform for dynamically controlling impact sensitivity without compromising performance.

The temperature at which inorganic oxidizers evolve oxygen is a key operational constraint in applications ranging from energetic materials to chemical oxygen generators and life-support systems. However, commonly used chlorates and perchlorates typically decompose at temperatures exceeding 400 °C, imposing limitations on efficiency, thermal management, and materials compatibility and motivating strategies for lower-temperature oxygen release without sacrificing yield. Here, porous Ni-based metal–organic frameworks catalyze LiClO₄ decomposition, lowering oxygen evolution onset temperatures by up to 180 °C relative to pure LiClO₄ while preserving >95 mol% O₂ yield. Framework porosity enables oxidizer melt-infiltration and promotes intimate nanoscale oxidizer-catalyst contact, enhancing catalytic effectiveness relative to the most effective nonporous Ni catalyst identified through Ni-salt screening. This approach demonstrates how framework porosity can be leveraged to enhance oxidizer-catalyst interactions and improve catalytic efficiency in oxygen-generating systems through structural design rather than solely through metal identity or loading, enabling lower-temperature oxygen release without compromising oxygen yield.

Metal–organic frameworks (MOFs) have emerged as promising candidates for quantum information and photonic applications due to their structural tunability and the potential to contain molecular qubits in architectures that support coherent light–matter interactions. In this study, we investigate the ultrafast coherent dynamics of a perylene-based MOF, UMCM-313, and its corresponding perylene-based organic linker crystal using time-resolved two-photon near-field scanning optical microscopy (NSOM). By tracking the electronic quantum coherence, we reveal coherent modes persisting up to several hundred femtoseconds (fs) at room temperature and extending to the picosecond regime (≈0.9–1 ps) at 173 K in the MOF, significantly longer than the coherence time observed in the organic linkers at the femtosecond scale. The enhanced electronic coherence of UMCM-313 is attributed to periodic chromophore separation and a reduced degree of homogeneous broadening. Because electron spin coherence can be several orders of magnitude longer than optical coherence, we further probed the spin coherence of photoexcited triplet states in UMCM-313 by using time-resolved and pulsed electron paramagnetic resonance (TREPR and pulse-EPR) spectroscopy. TREPR spectra reveal multiple triplet species within the framework, while pulse-EPR measurements yield a phase memory time of 237 ± 5 ns at 173 K. These results demonstrate that UMCM-313 supports both extended excitonic coherence and nanosecond spin coherence, underscoring the importance of periodic framework connectivity in sustaining phase-stable quantum states. The coexistence of electronic coherence and long-lived spin coherence highlights the potential of MOFs as hybrid platforms for quantum photonic and spintronic technologies capable of maintaining coherence under operationally accessible conditions.