Yingbo Zhao

Linear porous organic polymers (L-POPs) are rare species within the broad family of POPs due to the complexity of molecular design for preserving intrinsic free volume. With the absence of rigid structural unit, relaxed polymer chains undergo aggregation and dense packing, severely limiting the specific surface area. As a result, the preparation of L-POPs remains a formidable challenge. Herein, we overcome the above limitation by introducing a framework-imprint synthesis (FIS) strategy that exploits a sacrificial crystalline metal–organic framework (MOF) as a pore template. Specifically, triazolate L-POPs with flexible monomers are constructed via azide–alkyne click reaction within the confined nanochannels of the MOF host. The as-synthesized L-POP nanoparticles retain the octahedral morphology upon removal of the MOF scaffold. This process yields abundant hierarchical porosity comprising both micropores and mesopores, driven by the spatially organizing of polymer chains, which are impossible through solvothermal polymerization.

Porous crystalline organic materials have largely relied on macrocycles as topological rings to maintain porosity, which restricts the degree-of-freedom for structural dynamics and demands delicate synthetic control to avoid amorphous kinetic products. Here, we report rectilinear organic frameworks (ROFs) as a new class of crystalline porous materials composed of orderly packed linear polymer chains that can overcome the reliance on macrocycles. We synthesized twelve ROFs via linear polycondensation, nine of which resolved to atomic precision using electron diffraction. Their porosity emerges entirely from specific uniaxial or biaxial chain packing, governed by backbone stiffness and pendant groups that collaboratively frustrate dense packing. Linker elongation results in pore expansion, demonstrating modular material design and providing ROFs capable of gas separation. This macrocycle-free design enables efficient room-temperature scale-up, and structural transformations fundamentally unavailable to conventional frameworks. For a biaxial ROF, water adsorption triggers a coherent global rearrangement of chains, giving hydrogen-bonded water channels with high proton conductivity. Furthermore, we develop a crystal structure prediction method suitable for one-dimensional structures to analyze the energy landscape of ROFs and facilitating their rational design. Ultimately, ROFs establish a critical link between conventional linear polymers and reticular frameworks, providing a versatile platform for advanced porous materials.

Glasses linked by molecular building blocks are emerging materials promising for combining the processability of glasses and designability of reticular frameworks. Achieving modular chemical space construction is key to promoting structural diversity for these glasses, which requires systematically understanding their structures and properties. Herein, we combine rheological, thermal, compositional and total scattering techniques to study glasses and liquids based on titanium, zirconium and boron nodes, multi-dentate alcohol linkers and monodentate alcohol modulators and elucidate their structure-property relationships. With decreasing modulator, the node-linker-modulator series show increased connectivity characterized by increased viscosity and diminished heat capacity jump at glass transition, eventually giving glassy coordinative networks. By systematically tuning their compositions, we show the glass transition temperatures of these materials are affected by the interplay between non-covalent interactions and covalent network formation. The modular designability in alkoxide-based glasses is exploited for synthesizing fluorescent molecular network-forming glasses with high quantum yield, which can be integrated into electroluminescent devices. The current development represents an important expansion of reticular chemistry into the regime of glassy materials.

Vitrifying crystalline metal-organic frameworks (MOFs) is an emerging route to creating processable glassy materials with novel functions. However, a vast portion of MOFs, such as seminal MOF-5, are constructed from rigid aromatic dicarboxylate linkers. While essential for reticular design, these aromatic dicarboxylate linkers impart low configurational entropy, which has historically precluded the vitrification of a major portion of MOFs. Here, we report a generalizable strategy to overcome this limitation by synergistically promoting configurational degree of freedom, which combines grafting flexible side chains onto the rigid linkers, employing mixed-metal nodes, and introducing coordination modulators to tune network connectivity. This strategy is demonstrated by successfully vitrifying functionalized MOF-5 and MIL-101, producing a series of glasses with tunable properties controlled by the modulator content and metal composition. The resulting glasses exhibit promising functional properties, including high photoluminescence quantum yields, uniformity, and robustness as a host matrix for optically pumped lasers. This work establishes rational design principles for converting rigid MOFs into glassy materials, unlocking a vast library of reticular structures for the development of new functional glasses.

Halide solid-state electrolytes are promising for next-generation all-solid-state lithium-ion batteries due to their high ionic conductivity and wide electrochemical windows. While most research focuses on close-packed crystal structures, nonclose-packed frameworks─exemplified by UCl₃-type structures─offer unique advantages in enhancing lithium-ion transport via reduced diffusion barriers. Here, we report a new family of UCl₃-type crystalline oxychloride electrolytes, Li_0.388+xLa_0.475Ta_0.238Cl_3-xO_x (0 ≤ x ≤ 0.388, LLTCO), synthesized via rapid high-energy shake milling. The material with an optimized composition (x = 0.15) exhibits high ionic conductivity above 2 mS cm^-1 at 30 °C, oxidative stability exceeding 5 V vs Li/Li⁺, and excellent mechanical compressibility. Moreover, the LLTCO-based Li-Li symmetric cells show a long cycle life, indicating their strong capacity to suppress lithium dendrite formation. Spectroscopy analyses reveal the successful incorporation of oxygen, which preferentially substitutes Cl^- around Ta⁵⁺ sites without compromising crystallinity, even at a high oxygen content. The oxygen incorporation further promotes the formation of Li environments with fast dynamics, accounting for the enhanced conductivity. All-solid-state batteries utilizing the optimized oxychloride electrolyte in conjunction with Ni-rich cathodes demonstrate enhanced reversible capacities compared to their undoped counterparts. This work highlights the benefits of nonclose-packed UCl₃-type oxychloride electrolytes, offering new design strategies for high-performance all-solid-state batteries.

Amorphous porous organic polymers (POPs) are promising filler materials for mixed matrix membranes (MMMs). However, it is challenging to synthesize nanosized, monodispersed POP colloidal particles (CPs) suitable for membrane fabrication. Here, well-defined octahedral POP CPs with imine, ketone, or amine linkages were synthesized using octahedral MOF particles as sacrificial templates. In addition to shape replication, the MOF template also played a substantial role in spatially organizing polymer chains, resulting in highly porous POPs that are unattainable through bulk polymerization. For the first time, the mechanical properties of a single POP CP was examined by quantitative in situ compression testing under a scanning electron microscope. Introducing imine-linked POP CPs into a polyimide matrix led to a series of pure-organic defect-free MMMs exhibiting excellent homogeneity and flexibility. As a result, increasing the loading of POP in MMMs led to a stepwise increase in CO₂ permeability with largely unchanged CO₂/N₂ and CO₂/CH₄ selectivity.

The construction of a thin stable shell to encapsulate perovskite with effective carrier transport is a promising strategy to fabricate highly efficient and stable perovskite based optoelectronic devices. However, it is generally difficult to control the thickness and location of the encapsulating materials, ideally on perovskite grains. In this work, we developed a one-step method for the growth of titanium alkoxide networks in-situ in perovskite film forming an encapsulating layer on perovskite nanograin homogeneously. The thin encapsulating network brings much enhanced stability and allows effective carrier transport simultaneously. Light emitting diode based on this composite shows much enhanced stability under continuous operation.

Photoinduced proton transfer is an essential photochemical process for designing photocatalysts, white light emitters, bioimaging, and fluorescence sensing materials. However, deliberate control of the excited/ground states and meticulous manipulation of the excited state intramolecular proton transfer (ESIPT) pathway constitute a significant challenge in liquids and dense solids. Here, we present the integration of a hydronaphthoquinone fluorophore into a crystalline, porous, phototautomeric dynamic 3D covalent organic framework (COF) to show guest-induced fluorescence turn-on, emission redshift enhancement, and shortened lifetimes for ratiometric fluorescence humidity sensing. Theoretical and spectroscopic studies provide mechanistic insights into the conformational dynamics, charge transfer coupled with local excitation, and ground-state uphill regulation for the multiple tautomers. We illustrate the sensitive, rapid, steady, and self-calibrated ratiometric fluorescence sensing for a wide range of humidity benefiting from the architectural and chemical robustness and crystallinity of such a phototautomeric 3D COF. These findings provide molecular insights into the design of functional porous materials that integrate host-guest mutual recognition and photoelectronic response for multiplex molecular sensing for environmental monitoring and biomedical diagnostics applications.

The structural characterization of new materials often poses immense challenges, especially when obtaining single-crystal structures is difficult, which is a common difficulty with covalent organic frameworks (COFs). Despite this, understanding the atomic structure is crucial as it provides insights into the arrangement and connectivity of organic building blocks, offering the opportunity to establish the correlation of structure-function relationships and unravel material properties. In this study, we present an approach for determining the structures of COFs, an integration of electron crystallography and computational intelligence (COF+). By applying established chemistry knowledge and employing particle swarm optimization (PSO) for trial structure generation, we overcome existing limitations, thus paving the way for advancements in COF structural determination. We have successfully implemented this technique on four representative COFs, each with unique characteristics. These examples underline the accuracy and efficacy of our approach in addressing the challenges tied to COF structural determination. Furthermore, our approach has revealed new structure candidates with different topologies or interpenetrations that are chemically feasible. This discovery demonstrates the capability of our algorithm in constructing trial COF structures without being influenced by topological factors. Our new approach to COF structure determination represents a significant advancement in the field and opens new avenues for exploring the properties and applications of COF materials.