### Recent Submissions

• #### Layer number dependent ferroelasticity in 2D Ruddlesden–Popper organic-inorganic hybrid perovskites

(Nature Communications, Springer Science and Business Media LLC, 2021-02-26) [Article]
AbstractFerroelasticity represents material domains possessing spontaneous strain that can be switched by external stress. Three-dimensional perovskites like methylammonium lead iodide are determined to be ferroelastic. Layered perovskites have been applied in optoelectronic devices with outstanding performance. However, the understanding of lattice strain and ferroelasticity in layered perovskites is still lacking. Here, using the in-situ observation of switching domains in layered perovskite single crystals under external strain, we discover the evidence of ferroelasticity in layered perovskites with layer number more than one, while the perovskites with single octahedra layer do not show ferroelasticity. Density functional theory calculation shows that ferroelasticity in layered perovskites originates from the distortion of inorganic octahedra resulting from the rotation of aspherical methylammonium cations. The absence of methylammonium cations in single layer perovskite accounts for the lack of ferroelasticity. These ferroelastic domains do not induce non-radiative recombination or reduce the photoluminescence quantum yield.
• #### Single-Crystalline Ultrathin 2D Porous Nanosheets of Chiral Metal–Organic Frameworks

(Journal of the American Chemical Society, American Chemical Society (ACS), 2021-02-23) [Article]
Two-dimensional (2D) materials with highly ordered in-plane nanopores are crucial for numerous applications, but their rational synthesis and local structural characterization remain two grand challenges. We illustrate here that single-crystalline ultrathin 2D MOF nanosheets (MONs) with intrinsic porosity can be prepared by exfoliating layered metal-organic frameworks (MOFs), whose layers are stabilized by sterically bulky groups. As a result, three three-dimensional (3D) isostructural lanthanide MOFs possessing porous layer structures are constructed by coordinating metal ions with an angular dicarboxylate linker derived from chiral 1,1'-biphenyl phosphoric acid with pendant mesityl groups. The Eu-MOF is readily ultrasonic exfoliated into single-crystalline nanosheets with a thickness of ca. 6.0 nm (2 layers) and a lateral size of 1.5 × 3.0 μm2. The detailed structural information, i.e., the pore channels and individual organic and inorganic building units in the framework, is clearly visualized by a low-dose high-resolution transmission electron microscopy (HRTEM) technique. Benefiting from their ultrathin feature, the nanosheets are well embedded into the polymer matrix to form free-standing mixed-matrix membranes. In both the solution and membrane phase, the fluorescence of the MONs can be effectively quenched by a total of 17 chiral terpenes and terpenoids through supramolecular interactions with uncoordinated chiral phosphoric acids, leading to a chiral optical sensor for detecting vapor enantiomers, which is among the most challenging molecular recognition tasks.
• #### A Robust, Safe, and Scalable Magnetic Nanoparticle Workflow for RNA Extraction of Pathogens from Clinical and Wastewater Samples

(Global Challenges, Wiley, 2021-02-22) [Article]
Molecular diagnosis and surveillance of pathogens such as SARS-CoV-2 depend on nucleic acid isolation. Pandemics at the scale of COVID-19 can cause a global shortage of proprietary commercial reagents and BSL-2 laboratories to safely perform testing. Therefore, alternative solutions are urgently needed to address these challenges. An open-source method, magnetic-nanoparticle-aided viral RNA isolation from contagious samples (MAVRICS), built upon readily available reagents, and easily assembled in any basically equipped laboratory, is thus developed. The performance of MAVRICS is evaluated using validated pathogen detection assays and real-world and contrived samples. Unlike conventional methods, MAVRICS works directly in samples inactivated in phenol-chloroform (e.g., TRIzol), thus allowing infectious samples to be handled safely without biocontainment facilities. MAVRICS allows wastewater biomass immobilized on membranes to be directly inactivated and lysed in TRIzol followed by RNA extraction by magnetic nanoparticles, thereby greatly reducing biohazard risk and simplifying processing procedures. Using 39 COVID-19 patient samples and two wastewater samples, it is shown that MAVRICS rivals commercial kits in detection of SARS-CoV-2, influenza viruses, and respiratory syncytial virus. Therefore, MAVRICS is safe, fast, and scalable. It is field-deployable with minimal equipment requirements and could become an enabling technology for widespread testing and wastewater monitoring of diverse pathogens.
• #### Exfoliation of surfactant swollen layered MWW zeolites into two-dimensional zeolite nanosheets using telechelic liquid polybutadiene

(Microporous and Mesoporous Materials, Elsevier BV, 2021-02) [Article]
Two-dimensional (2D) zeolites have the potential to enhance mass transport by reducing diffusion lengths and thus find applications in catalysis and separation. High aspect ratio 2D zeolite nanosheets are required for fabrication of thin, high-flux zeolite membranes. Preparation of 2D zeolite nanosheets can be achieved by exfoliation of layered zeolite precursors, which usually requires multiple steps including swelling with cationic surfactants, exfoliation by applying a mechanical force such as shearing or sonication, purification and removal of the surfactants. The exfoliation of surfactant swollen layered zeolite precursors has been studied using molten polystyrene and telechelic liquid polybutadiene, but still requires extensive shearing force. Recently, a novel one-step exfoliation method has been developed for non-swollen MWW zeolite precursors using tetrabutylammonium hydroxide (TBAOH) solution. In this work, we study the exfoliation of surfactant swollen MWW layered precursors (with and without aluminum) in commercially available liquid hydroxyl-terminated polybutadiene (HTPB) with the aim to provide fundamental understanding of the interaction between the liquid polybutadiene and the surfactant swollen layered zeolite precursors. It was found that surfactant swollen ITQ-1, (ITQ-1(S)), a pure silica layered precursor with MWW framework after being swollen with a cationic surfactant, can be exfoliated in liquid HTPB at room temperature without applying any additional shearing force. The aluminum containing surfactant swollen MWW precursors can be also exfoliated in HTPB at room temperature, but require additional shearing forces. The exfoliation process was monitored using rheology experiments and studied by tuning the composition of the zeolite precursors. The interaction between the layered zeolite precursor and the hydroxyl group of the liquid polybutadiene allows the polymer to intercalate the precursor and exfoliate it into nanosheets. The presence of framework aluminum and the nature of the organic structure directing agents (OSDAs) are key parameters affecting the exfoliation process. Framework Al is unfavorable for the exfoliation possibly due to the surface charges introduced by the aluminum. Bulky OSDA, trimethyladamantammonium (TMAda+), in the interlayer spacing may facilitate the exfoliation.
• #### Coordination-based self-assembled capsules (SACs) for protein, CRISPR–Cas9, DNA and RNA delivery

(Chemical Science, Royal Society of Chemistry (RSC), 2021-02-01) [Article]
SACs can be efficiently used to load biologics such as proteins, CRISPR–Cas9, DNA and RNA and release them on-demand.
• #### Penetrant competition and plasticization in membranes: How negatives can be positives in natural gas sweetening

(Journal of Membrane Science, Elsevier BV, 2021-02) [Article]
Membranes are attractive for upgrading natural gas; however, the gas permeation processes through membranes are challenging to control. The coexistence of condensable H2S and CO2 typically causes membrane performance to decline under practical feed conditions, due to uncontrolled penetrate competition and undesired plasticization of the membrane polymer matrix. In this paper, we report a strategy to successfully transform these apparent negatives, i.e. plasticization and penetrate competition, into positives that boost the natural gas sweetening efficiency of membranes greatly. Our strategy is to disperse engineered metal organic framework (MOF) fillers into designed polymer matrices to form hybrid membranes, which promote the permeation of both H2S and CO2 but hinder CH4 permeation. Moreover, uniformly dispersed MOF fillers also significantly alter the plasticization responses of polymer matrices, enabling controlled plasticization benefits. Ultimately, we illustrate a highly tunable MOF-polymer hybrid membrane platform that meets the diverse natural gas sweetening requirements under aggressive conditions.
• #### Electrospun Adsorptive Nanofibrous Membranes from Ion Exchange Polymers to Snare Textile Dyes from Wastewater

(Advanced Materials Technologies, Wiley, 2021-01-27) [Article]
Increasing discharges of industrial wastewater, along with ever-stricter regulations for the protection of natural water sources, have amplified the demand for highly efficient water treatment technologies. Here, electrospun nanofibrous polyimides enhanced with ion exchange properties are proposed as adsorptive membranes for the treatment of dye-loaded textile wastewater. With the careful selection of monomers, carboxyl-functionalized porous polyimides are synthesized in a single step and then further decorated with strong cation and anion exchange side groups. Nuclear magnetic resonance spectroscopy and thermal gravimetric analysis are used to investigate the alkylation degree and total exchange capacity of the polymers. The electrospinning conditions are optimized to produce highly flexible membrane mats with a uniform nanofibrous structure. A series of dye sorption experiments on the nanofibrous membranes reveals the adsorption kinetics and the effects of the polyimide backbone, the charged side groups, and the hydrophilicity. A recycling study is conducted to confirm the stability of the adsorbent membranes. The results suggest that nanofibrous polyimide membranes enhanced with ion exchange properties are promising candidates for the treatment of dye-laden wastewater. Owing to their facile syntheses and unique properties, these membranes show promising potential in environmental applications.
• #### Sustained and targeted delivery of checkpoint inhibitors by metal-organic frameworks for cancer immunotherapy

(Science Advances, American Association for the Advancement of Science (AAAS), 2021-01-22) [Article]
The major impediments to the implementation of cancer immunotherapies are the sustained immune effect and the targeted delivery of these therapeutics, as they have life-threatening adverse effects. In this work, biomimetic metal-organic frameworks [zeolitic imidazolate frameworks (ZIFs)] are used for the controlled delivery of nivolumab (NV), a monoclonal antibody checkpoint inhibitor that was U.S. Food and Drug Administration–approved back in 2014. The sustained release behavior of NV-ZIF has shown a higher efficacy than the naked NV to activate T cells in hematological malignancies. The system was further modified by coating NV-ZIF with cancer cell membrane to enable tumor-specific targeted delivery while treating solid tumors. We envisage that such a biocompatible and biodegradable immunotherapeutic delivery system may promote the development and the translation of hybrid superstructures into smart and personalized delivery platforms.
• #### Multiscale Assembly of [AgS 4 ] Tetrahedrons into Hierarchical Ag–S Networks for Robust Photonic Water

There is an urgent need to assemble ultrasmall metal chalcogenides (with atomic precision) into functional materials with the required anisotropy and uniformity, on a micro- or even macroscale. Here, a delicate yet simple chemistry is developed to produce a silver-sulfur network microplate with a high monodispersity in size and morphology. Spanning from the atomic, molecular, to nanometer, to micrometer scale, the key structural evolution of the obtained microplates includes 2D confinement growth, edge-sharing growth mode, and thermodynamically driven layer-by-layer stacking, all of which are derived from the [AgS<sub>4</sub> ] tetrahedron unit. The key to such a high hierarchical, complex, and accurate assembly is the dense deprotonated ligand layer on the surface of the microplates, forming an infinite surface with high negative charge density. This feature operates at an orderly distance to allow further hierarchical self-assembly on the microscale to generate columnar assemblies composed of microplate components, thereby endowing the feature of the 1D photonic reflector to water (i.e., photonic water). The reflective color of the resulting photonic water is highly dependent on the thickness of the building blocks (i.e., silver-sulfur microplates), and the coexistent order and fluidity help to form robust photonic water.
• #### Artificial channels for confined mass transport at the sub-nanometre scale

(Nature Reviews Materials, Springer Science and Business Media LLC, 2021-01-21) [Article]
Mass transport at the sub-nanometre scale, including selective transport of gases, liquids and ions, plays a key role in systems such as catalysis, energy generation and storage, chemical sensing and molecular separation. Highly efficient biological channels in living organisms have inspired the design of artificial channels with similar, or even higher, mass-transport efficiency, which can be used at a much larger scale. In this Review, we highlight synthetic-nanomaterials-enabled channels in the platforms of well-defined nanopores, 1D nanotubes and 2D nanochannels, and discuss their design principles, channel architectures and membrane or device fabrication. We focus on fundamental mechanisms of sub-nanometre confined mass transport and their relationships with the structure–property–performance. We then present the practicalities of these channels and discuss their potential impact on the development of next-generation sustainable technologies for use in applications related to energy, the environment and healthcare.
• #### Coating of Conducting and Insulating Threads with Porous MOF Particles through Langmuir-Blodgett Technique

(Nanomaterials, MDPI AG, 2021-01-10) [Article]
• #### Inquiry for the multifunctional design of metal–organic frameworks: in situ equipping additional open metal sites (OMSs) inducing high CO2 capture/conversion abilities

(Materials Chemistry Frontiers, Royal Society of Chemistry (RSC), 2021) [Article]
On the basis of $\textit{in situ}$ fabricating multifunctional MOFs, a binuclear Co-MOF with open cobalt sites was accomplished. The multifunctional sites afforded increased CO$_{2}$ uptake, together with the synergistic catalysis in promoting the CO$_{2}$ conversion.
• #### Noble metal nanowire arrays as an ethanol oxidation electrocatalyst

(Nanoscale Advances, Royal Society of Chemistry (RSC), 2021) [Article]
Vertically aligned noble metal nanowire arrays were grown on conductive electrodes based on a solution growth method. They show significant improvement of electrocatalytic activity in ethanol oxidation, from a re-deposited sample of the same detached nanowires. The unusual morphology provides open diffusion channels and direct charge transport pathways, in addition to the high electrochemically active surface from the ultrathin nanowires. Our best nanowire arrays exhibited much enhanced electrocatalytic activity, achieving a 38.0 fold increase in specific activity over that of commercial catalysts for ethanol electrooxidation. The structural design provides a new direction to enhance the electrocatalytic activity and reduce the size of electrodes for miniaturization of portable electrochemical devices.
• #### Unprecedented gas separation performance of a difluoro-functionalized triptycene-based ladder PIM membrane at low temperature

(Journal of Materials Chemistry A, Royal Society of Chemistry (RSC), 2021) [Article]
A novel fluorinated triptycene-derived ladder PIM (DFTTB) showed an unprecedented O$_{2}$/N$_{2}$ selectivity of 10.1 and O$_{2}$ permeability of 137 barrer at −30 °C that provides new opportunities for low temperature air separation applications.
• #### Surface engineering of intrinsically microporous poly(ether-ether-ketone) membranes: From flat to honeycomb structures

(Journal of Membrane Science, Elsevier BV, 2020-12-25) [Article]
Surface engineering of polymeric membranes can induce subtle changes in membrane properties and enhance their performance. Numerous membrane surface modification methods have been developed to improve the material performance. However, these methods can be complex, thus limiting their practical applications. Herein, we present a simple method for fabricating membranes with honeycomb surfaces by controlling the polymer molecular weight (Mw). Spirobisindane-based intrinsically microporous poly(ether-ether-ketone) (iPEEK-SBI) homopolymers with low and high Mws were synthesized and used to prepare organic solvent nanofiltration (OSN) membranes. The significant effects of polymer Mw on its physical properties, membrane morphology, and OSN performance were systematically investigated. iPEEK showed excellent solution processability, high Brunauer–Emmett–Teller surface area, and remarkable thermal stability. Three mechanically flexible OSN membranes exhibiting honeycomb surfaces with different honeycomb cell sizes were prepared using iPEEK-SBI homopolymers with low Mws at concentrations of 27–39 wt% in N-methyl-2-pyrrolidone. By contrast, the use of iPEEK-SBI homopolymers with high Mws yielded membranes with flat surfaces. The Mw cutoffs of the membranes were fine-tuned in the range of 408–772 g mol−1 by adjusting the dope solution concentration. Although the Mw cutoffs were unaffected by polymer Mw, the membranes derived from the polymer with low Mw exhibited substantially higher solvent permeance (18%–26%) than that of the high Mw membrane prepared at the same dope solution concentration. Stable performance was demonstrated over seven days of continuous cross-flow filtration and a six-month aging of the membranes. This work shows the importance of surface engineering for OSN membranes by adjusting polymer Mw. These findings open a new avenue for fine-tuning the properties of OSN membranes.
• #### Calix[4]pyrrole-Crosslinked Porous Polymeric Networks for Micropollutant Removal from Water.

(Angewandte Chemie (International ed. in English), Wiley, 2020-12-23) [Article]
Three calix[4]pyrrole-based porous organic polymers (P1-P3) have been prepared with the goal of removing organic micropollutants from water. A bowl-shaped α,α,α,α-tetraalkynyl calix[4]pyrrole and diketopyrrolopyrrole monomer were crosslinked via Sonogashira coupling to produce a three-dimensional network polymer P1. This polymer, which proved too hydrophobic for use as an adsorbent, was converted to the corresponding neutral polymer P2 (containing carboxylic acid groups) and its anionic derivative (polymer P3 containing carboxylate anion groups) through post-polymerization structural modification of the pendent tert-butyl esters. The anionic polymer P3 outperformed its precursor neutral polymer P2 as determined from screening studies involving a variety of model organic micropollutants of different charge, hydrophilicity and functionality, including dyes, simple aromatics, and two cationic pesticides. Polymer P3 proved particularly effective for cationic micropollutants. The theoretical maximum adsorption capacity (qmax,e) of P3 determined from the corresponding Langmuir isotherms reached 454 mg g-1 for the dye methylene blue, 344 mg g-1 for the pesticide paraquat, and 495 mg g-1 for diquat, respectively. These uptake values are signiﬁcantly higher than those of most synthetic adsorbent materials reported to date. The present findings thus lend support to the conclusion that calix[4]pyrrole-based porous organic polymers may have a role to play in water puriﬁcation.
• #### Intrinsically Porous Molecular Materials (IPMs) for Natural Gas and Benzene Derivatives Separations

(Accounts of Chemical Research, American Chemical Society (ACS), 2020-12-17) [Article]
Separating and purifying chemicals without heat would go a long way toward reducing the overall energy consumption and the harmful environmental footprint of the process. Molecular separation processes are critical for the production of raw materials, commodity chemicals, and specialty fuels. Over 50% of the energy used in the production of these materials is spent on separation and purification processes, which primarily includes vacuum and cryogenic distillations. Chemical manufacturers are now investigating modest thermal approaches, such as membranes and adsorbent materials, as they are more cognizant than ever of the need to save energy and prevent pollution. Porous materials, such as zeolites, metal–organic frameworks (MOFs), and covalent organic frameworks (COFs), have dominated the field of industrial separations as their high surface areas and robust pores make them ideal candidates for molecular separations of gases and hydrocarbons. Separation processes involving porous materials can save 70%–90% of energy costs compared to that of thermally driven distillations. However, most porous materials have low thermal, chemical, and moisture stability, in addition to limited solution processability, which tremendously constrain their broad industrial translation. Intrinsically porous molecular materials (IPMs) are a subclass of porous molecular materials that are comprised of molecular host macrocycles or cages that absorb guests in or around their intrinsic cavity. IPMs range from discrete porous molecules to assemblies with amorphous or highly crystalline structures that are held together by weak supramolecular interactions. Compared to the coordination or dynamic covalent bond-constructed porous frameworks, IPMs possess high thermal, chemical, and moisture stability and maintain their porosity under critical conditions. Moreover, the intrinsic porosity endows IPMs with excellent host–guest properties in solid, liquid (organic or aqueous), and gas states, which can be further utilized to construct diverse separation strategies, such as solid–gas adsorption, solid–liquid absorption, and liquid–liquid extraction. The diversity of host–guest interactions in the engineered IPMs affords a plethora of possibilities for the development of the ideal “molecular sieves”. Herein, we present a different take on the applicability of intrinsically porous materials such as cyclodextrin (CD), cucurbiturils (CB), pillararene (P), trianglamines (T), and porous organic cages (POCs) that showed an impressive performance in gas purification and benzene derivatives separation. IPMs can be easily scaled up and are quite stable and solution processable that consequently facilitates a favorable technological transformation from the traditional energy-intensive separations. We will account for the main advances in molecular host–guest chemistry to design “on-demand” separation processes and also outline future challenges and opportunities for this promising technology.
• #### Intermediate Binding Control Using Metal–Organic Frameworks Enhances Electrochemical CO2 Reduction

(Journal of the American Chemical Society, American Chemical Society (ACS), 2020-12-15) [Article]
In the electrochemical CO2 reduction reaction (CO2RR), control over the binding of intermediates is key for tuning product selectivity and catalytic activity. Here we report the use of reticular chemistry to control the binding of CO2RR intermediates on metal catalysts encapsulated inside metal–organic frameworks (MOFs), thereby allowing us to improve CO2RR electrocatalysis. By varying systematically both the organic linker and the metal node in a face-centered cubic (fcu) MOF, we tune the adsorption of CO2, pore openness, and Lewis acidity of the MOFs. Using operando X-ray absorption spectroscopy (XAS) and in situ Raman spectroscopy, we reveal that the MOFs are stable under operating conditions and that this tuning plays the role of optimizing the *CO binding mode on the surface of Ag nanoparticles incorporated inside the MOFs with the increase of local CO2 concentration. As a result, we improve the CO selectivity from 74% for Ag/Zr-fcu-MOF-1,4-benzenedicarboxylic acid (BDC) to 94% for Ag/Zr-fcu-MOF-1,4-naphthalenedicarboxylic acid (NDC). The work offers a further avenue to utilize MOFs in the pursuit of materials design for CO2RR.
• #### Synthesis of Polycarboxylate Rh(II)-Metal-Organic Polyhedra and their use as Building Blocks for Highly-Connected Metal-Organic Frameworks.

(Angewandte Chemie (International ed. in English), Wiley, 2020-12-11) [Article]
Use of preformed metal-organic polyhedra (MOPs) as supermolecular building blocks (SBBs) for the synthesis of metal-organic frameworks (MOFs) remains underexplored due to lack of robust functionalized MOPs. Herein we report the use of polycarboxylate cuboctahedral Rh(II)-MOPs for constructing highly-connected MOFs. Cuboctahedral MOPs were functionalized with carboxylic acid groups on their 12 vertices or 24 edges through coordinative or covalent post-synthetic routes, respectively. We then used each isolated polycarboxylate Rh(II)-MOP as 12-c cuboctahedral or 24-c rhombicuboctahedral SBBs that, upon linkage with metallic secondary building units (SBUs), afford bimetallic highly-connected MOFs. The assembly of a pre-synthesized 12-c SBB with a 4-c paddle-wheel SBU, and a 24-c SBB with a 3-c triangular Cu(II) SBU gave rise to bimetallic MOFs having ftw (4,12-c) or rht (3,24-c) topologies, respectively.