Dual-porous ZIF-8 heterogeneous catalysts with increased reaction sites for efficient PET glycolysis.

Poly (ethylene terephthalate) (PET) has been widely used for drink bottles, food packing, films, and fibers, resulting in millions of tons of waste PET. Less than 10% of that waste is recycled, and the rest is discarded or incinerated. Waste PET upcycling employs chemical recycling and particularly glycolysis to create the bis(2-hydroxyethyl) terephthalate (BHET) monomer. Herein, we report a dual-porous zeolitic imidazolate framework-8 nanoparticle (DPZIF-8) heterogeneous catalyst for efficient PET glycolysis. The DPZIF-8 nanoparticles were prepared using a triethylamine modulator, which can control the nucleation and growth mechanisms of the ZIF-8 nanoparticles. The DPZIF-8 nanoparticles include both intrinsic micropores and particle-particle adhesion-induced mesopores that can provide a larger external surface area of the zinc sites in the ZIF-8 architecture. The PET glycolysis catalyzed by DPZIF-8 at 180 °C and 1 atm for 4 h shows a PET conversion of 91.7% and a BHET yield of 76.1%, the latter particularly being much higher than with a traditional heterogeneous ZIF-8 catalyst. This dual-porous structure rational design strategy can be versatile for other metal-organic frameworks (MOFs) to increase the interfacial catalytic reaction sites between the metal-organic framework and the polymer, enhancing the PET depolymerization performance and efficiency.

Hydroxyl-functionalized microporous polymer membranes with tunable para position substituent benzaldehydes for gas separation.

We report hydroxyl-functionalized microporous polymers with tunable benzaldehyde groups for gas separation membranes. These polymers were synthesized via acid-catalyzed Friedel-Crafts polycondensation. The tunability in d-spacing and fractional free volume of these polymers depends on the para position substituents (-H, -F, -Cl, and -Br) of the benzaldehyde. Specifically, the size and polarity of the para position substituent influence the polymer chain-packing structure. Consequently, the hydroxyl-functionalized microporous polymer membrane with a larger para position substituent in the benzaldehyde group exhibited improved gas permeability. This improvement is due to enhanced gas diffusivity resulting from the inefficient polymer chain-packing structure. Furthermore, these membranes demonstrated enhanced CO2 plasticization resistance, attributable to the rigid, contorted polymer structure and the hydrogen bonding interactions between hydroxyl groups. This study provides insights into the relationship between the polymer chain-packing structure, tunable para position substituents, and molecular transport.

Ionic Cross-Linked MOF-Polymer Mixed-Matrix Membranes for Suppressing Interfacial Defects and Plasticization Behavior.

To address the plasticization phenomenon and MOF-polymer interfacial defects, we report the synthesis of ionic cross-linked MOF MMMs from a dual brominated polymer and MOF components by using N,N'-dimethylpiperazine as the cross-linker. We synthesized brominated MIL-101(Cr) nanoparticles by using mixed linkers and prepared brominated polyimide (6FDA-DAM-Br) to form ionic cross-linked MMMs. The gas permeation properties of the polyimide, ionic cross-linked MOF-polymer MMMs, and non-cross-linked MOF-polymer MMMs with various MOF weight loadings were investigated systematically to effectively understand the effects of MOF weight loading and ionic cross-linking. The ionic cross-linked 40 wt % MOF-polymer MMM exhibited significantly enhanced gas permeability with an H2 permeability of 1640 Barrer and CO2 permeability of 1981 Barrer and slightly decreased H2/CH4, H2/N2, CO2/CH4 and CO2/N2 selectivities of 16.9, 15.4, 20.5, and 18.6, respectively. The H2 and CO2 permeabilities are approximately 2-3 fold higher than those of the pure polyimide (6FDA-DAM) membrane. Moreover, the ionic cross-linked 40 wt % MOF-polymer MMM exhibited significantly increased resistance to plasticization. This is because the brominated MOF incorporation boosted molecular transport and polymer chain rigidity, and ionic cross-linking further reduced the number of interfacial defects and polymer chain mobility.

Contents of the Standardized Suicide Prevention Program for Gatekeeper Intervention in Korea, Version 2.0.

OBJECTIVE: Suicide is a huge nationwide problem that incurs a lot of socio-economic costs. Suicide also inflicts severe distress on the people left behind. The government of the Republic of Korea has been making many policy efforts to reduce suicide rate. The gatekeeper program, 'Suicide CARE', is one of the meaningful modalities for preventing suicide. METHODS: Multidisciplinary research team collaborated to update the 'Suicide CARE' to version 2.0. RESULTS: In the 'Introductory part', the authors have the time to think about the necessity and significance of the program before conducting full-scale gatekeeper training. In the 'Careful observation' part, trainees learn how to understand and recognize the various linguistic, behavioral, and situational signals that a person shows before committing suicide. In the 'Active listening' part, trainees learn how to ask suicide with a value-neutral attitude as well listening empathetically. In the 'Risk evaluation and Expert referral' part, trainees learn intervening strategies to identify a person's suicidal intention, plan, and past suicide attempts, and connect the person to appropriate institutes or services. CONCLUSION: Subsequent studies should be conducted to verify the efficacy of the gatekeeper program.

"Suicide CARE" (Standardized Suicide Prevention Program for Gatekeeper Intervention in Korea): An Update.

OBJECTIVE: In 2011, "Suicide CARE" (Standardized Suicide Prevention Program for Gatekeeper Intervention in Korea) was originally developed for the early detection of warning signs of suicide completion, since there is a tendency to regard emotional suppression as a virtue of Korean traditional culture. A total of 1.2 million individuals completed the training program of "Suicide CARE" in Korea. METHODS: More sophisticated suicide prevention approaches according to age, sex, and occupation have been proposed, demanding for a more detailed revision of "Suicide CARE." Thus, during the period from August 2019 to February 2020, "Suicide CARE" has been updated to version 2.0. The assessments on domestic gatekeeper training programs for suicide prevention, international gatekeeper training programs for suicide prevention, psychological autopsy interview reports between 2015 and 2018, and the evaluation of feedback from people who completed "Suicide CARE" version 1.6 training were performed. RESULTS: We describe the revision process of "Suicide CARE," revealing that "Suicide CARE" version 2.0 has been developed using an evidence-based methodology. CONCLUSION: It is expected that "Suicide CARE" version 2.0 be positioned as the basic framework for many developing gatekeeper training programs for suicide prevention in Korea in the near future.