Interannual variability of extreme precipitation in late summer over west China during 1961–2021

The characteristics and related mechanisms of the interannual variability of late summer (August) extreme precipitation in West China (WC) were investigated from 1961 to 2021. Precipitation and extreme precipitation (defined as the 99th percentile) generally decreased in the southeast-northwest direction, with a maximum in the Sichuan Basin. The non-linear trends in extreme precipitation have increased since the 1980s. Therefore, we further found that the interannual increase in extreme precipitation in the WC was significantly related to the eastward-strengthened South Asian high, western-stretched Western Pacific Subtropical high, enhanced westerly jet, anomalous cyclone in Mongolia, and anomalous anticyclone in the western Pacific. The anti-cyclonic anomaly is a Gill-type response to increase the sea surface temperature in the western Pacific. A mid-high latitude barotropic Rossby-wave train can be induced and has essential effects on the above key circulation patterns, further cooperating with the strong updrafts rather than strengthening and maintaining extreme precipitation in the WC

Electroactive Covalent Organic Frameworks: Design, Synthesis, and Applications

International audienceCovalent organic frameworks (COFs) are an emerging class of crystalline porous polymers with tailorable compositions, porosities, functionalities and profound chemical stability. The manageable installation of electroactive moieties on the skeletons and pore walls of COFs transforms them into promising electroactive materials that are applicable for energy-related applications. Significant progresses have been made in the application of electroactive COFs for electrochemical energy storages and conversions. Herein, the recent advances in the design and application of electroactive COFs in capacitors, batteries, conductors, fuel-cells, water-splitting, and electrocatalysis are presented. Their remarkable performances are discussed and compared with other porous materials, while perspectives in development of electroactive COFs are also provided

Breaking Dynamic Behavior in 3D Covalent Organic Framework with Pre-Locked Linker Strategy

Due to their large surface area and pore volume, three-dimensional covalent organic frameworks (3D COFs) have emerged as competitive porous materials. However, structural dynamic behavior, often observed in imine-linked 3D COFs, could potentially unlock their potential application in gas storage. Herein, we showed how a pre-locked linker strategy introduces breaking dynamic behavior in 3D COFs. A predesigned planar linker-based 3,8-diamino-6-phenylphenanthridine (DPP) was prepared to produce non-dynamic 3D JUC-595, as the benzylideneamine moiety in DPP locked the linker flexibility and restricted the molecular bond rotation of the imine linkages. Upon solvent inclusion and release, the PXRD profile of JUC-595 remained intake, while JUC-594 with a flexible benzidine linker experienced crystal transformation due to framework contraction–expansion. As a result, the activated JUC-595 achieved higher surface areas (754 m2 g−1) than that of JUC-594 (548 m2 g−1). Furthermore, improved CO2 and CH4 storages were also seen in JUC-595 compared with JUC-594. Impressively, JUC-595 recorded a high normalized H2 storage capacity that surpassed other reported high-surface area 3D COFs. This works shows important insights on manipulating the structural properties of 3D COF to tune gas storage performance

Synthesis of zeolite SSZ-24 using a catalytic amount of SSZ-13 seeds

International audienc

MOF–cation exchange resin composites and their use for water decontamination

International audienc

Fast and efficient synthesis of SSZ-13 by interzeolite conversion of Zeolite Beta and Zeolite L

CERVOXY COLLInternational audienc

Structural and Optical Modulations in Covalent Organic Frameworks via Pressure-treated Engineering

Piezochromic materials, exhibiting outstanding pressure-responsive performance including pressure-induced emission en-hancement (PIEE), blue-shifted emission, white-light emitting and so on, are crucial in various fields such as in advanced sensing and smart photonics. Covalent organic frameworks (COFs), an emerging class of crystalline porous materials (CPMs), possess dynamic structures and adjustable photophysical properties, making them promising candidates for the development of piezochromic materials. Nevertheless, this area remains relatively understudied. In this study, a successful synthesis of a series of bicarbazole-based COFs with varying topologies, dimensions, and linkages was conducted, followed by an investigation of their structural and optical properties under hydrostatic pressure generated by a diamond anvil cell. Consequently, these COFs exhibited distinct piezochromic behaviors, particularly an astonishing PIEE phenomenon with a 16-fold increase in fluorescence intensity from three-dimensional COFs, surpassing the performance of CPMs and nearly all known organic small molecules with PIEE behavior. In contrast, two-dimensional COFs, with rigid and conjugated structures, typically showed red-shifted and reduced emission, while the flexible variants exhibited rare blue-shifted emission. Mecha-nism research further revealed that these different piezochromic behaviors were primarily determined by interlayer distance and interaction. This study represents the first systematic exploration of the structures and optical properties of COFs through pressure-treated engineering and provides a new perspective on the design of piezochromic materials

Carbon beads with a well-defined pore structure derived from ion-exchange resin beads

International audienc

A sponge-like small pore zeolite with great accessibility to its micropores

International audienceSmall pore zeolites, due to pore size constraint, have limited applications. Post-modification on the materials is therefore important to widen their use. A CHA-type zeolite (SSZ-13) with unique sponge-like structure is obtained by fluoride leaching. The development of macroporosity started from the crystal surfaces and continued progressively into the crystal by prolonging treatment. Nitrogen physisorption measurements showed an increase in micropore volume and specific surface area as a consequence of the dissolution of low crystalline part of the zeolite. The impact of etching on the accessiblity through the pore network, evaluated by means of breakthrough experiments of CO2/N2 and CO2/CH4 binary mixtures, showed an improved accessibility thanks to the interconnected macropores which shortens the diffusion pathlength. The set of experimental data shows the sponge-like SSZ-13 crystals retaining the intrinsic zeolitic properties but having an improve accessibility and crystallinity