Cascade exciton-pumping engines with manipulated speed and efficiency in light-harvesting porous π-network films

Introduction of Multicomponent Dyes into 2D MOFs: A Strategy to Fabricate White Light-Emitting MOF Composite Nanosheets

Metal-organic frameworks (MOFs) have been extensively studied in host-guest chemistry by means of ultrahigh porosities, tunable channels, and component diversities. As the host matrix, MOFs exhibit immense potential in the preparation of single-phase white light-emitting (SPWLE) materials. Nonetheless, it is a great challenge that the size of the introduced guest molecules is limited by MOF pores, which affects the WLE optimization. In this work, two-dimensional (2D) MOFs are first utilized as the host matrices to simultaneously encapsulate red-green-blue fluorescent dyes for SPWLE. Various dyes@2D MOF composites with high-quality WLE performances and ultrathin nanosheet morphologies are directly assembled from 2D MOF precursors and dyes in high yields. Owing to the flexible interlamellar space of 2D MOFs, different types and sizes of guests can be easily introduced, which greatly expands the range of available MOF hosts and guests, making the WLE much more tunable. The strategy of employing 2D MOFs as the host matrices to introduce multicomponent dyes for SPWLE nanosheets resolves the restriction of MOF pores on the guest molecule size and opens a new avenue to rationally design and prepare SPWLE nanosheets that are highly solution-processable.

Synergistic Engineering of Conduction Band, Conductivity, and Interface of Bilayered Electron Transport Layers with Scalable TiO2 and SnO2 Nanoparticles for High-Efficiency Stable Perovskite Solar Cells

A simple, synergistic engineering of the conduction band (CB), conductivity, and interface of TiO₂-based bilayered electron transport layers (ETLs) via scalable TiO₂ and SnO₂ nanoparticles processed at low temperature (≤ 100 °C) for regular planar perovskite solar cells (PSCs) was developed. The bottom layer (Lt-TiO₂:SnO₂ nanocomposite film) was prepared by spin coating from the ethanol suspension of small ground TiO₂ nanoparticles with big ground SnO₂ nanoparticles as the additive. The top C-SnO₂ layer (spin-coated from the concentrated commercial SnO₂ nanoparticles (C-SnO₂ NPs, 20 wt %, 7 nm in size suspended in H₂O)) can be regarded as an interlayer between Lt-TiO₂:SnO₂ and perovskite (Psk) absorbers. Bilayered Lt-TiO₂:SnO₂/C-SnO₂ ETLs are dense films with a cascade CB, good conductivity, facile electron extraction/transport ability, and a highly hydrophilic surface for depositing high-quality Psk films. Regular planar PSCs based on Lt-TiO₂:SnO₂/C-SnO₂ ETLs combined with a (FAI)_0.90(PbI₂)_0.94(MABr)_0.10(PbBr₂)_0.10 absorber and a spiro-OMeTAD hole transporter achieved the highest power conversion efficiency of 22.04% with a negligible current hysteresis. The champion cell lost less than 3% of the initial efficiency under continuous room lighting (1000 lux) for 1000 h (lost 10% after 2184 h) without encapsulation under an inert atmosphere. Four related low-temperature-processed ETLs (Lt-TiO₂/C-SnO₂, Lt-C-SnO₂, Lt-TiO₂:SnO₂, and Lt-TiO₂) were fabricated using the same metal oxide nanoparticle suspensions and studied simultaneously to reveal the function of each metal oxide in the bilayered Lt-TiO₂:SnO₂/C-SnO₂ ETLs. In the bottom Lt-TiO₂:SnO₂ layer, small TiO₂ nanoparticles were needed for making a dense film, and highly conducting big SnO₂ nanoparticles are used to increase the conductivity of ETLs and a handy electron transport path for reducing the charge accumulation and series resistance of the cell. A top C-SnO₂ layer (regarded as an interlayer between Psk and Lt-TiO₂:SnO₂) was used to extract/transport electrons facilely, to form a bilayered ETL with a cascade CB, and to create a hydrophilic surface to deposit high-quality Psk films to enhance the photovoltaic performance of the PSCs. This study provides a blueprint for designing good-performance ETLs for high-efficiency, stable regular planar PSCs using various sized nanoparticles prepared in a very simple and low-cost way.

Two-dimensional conjugated microporous polymer films: fabrication strategies and potential applications

This review describes the latest advances in the preparation and application of two-dimensional conjugated microporous polymers, as well as the future research directions of this field.

Electropolymerization of robust conjugated microporous polymer membranes for rapid solvent transport and narrow molecular sieving

Pore size uniformity is one of the most critical parameters in determining membrane separation performance. Recently, a novel type of conjugated microporous polymers (CMPs) has shown uniform pore size and high porosity. However, their brittle nature has prevented them from preparing robust membranes. Inspired by the skin-core architecture of spider silk that offers both high strength and high ductility, herein we report an electropolymerization process to prepare a CMP membrane from a rigid carbazole monomer, 2,2’,7,7’-tetra(carbazol-9-yl)-9,9’-spirobifluorene, inside a robust carbon nanotube scaffold. The obtained membranes showed superior mechanical strength and ductility, high surface area, and uniform pore size of approximately 1 nm. The superfast solvent transport and excellent molecular sieving well surpass the performance of most reported polymer membranes. Our method makes it possible to use rigid CMPs membranes in pressure-driven membrane processes, providing potential applications for this important category of polymer materials.

Conjugated microporous polymers (CMPs) have great potential in membrane applications but are often brittle. Here, the authors develop an electropolymerization process to form a skin-core architecture which allows them to overcome mechanical limitations while keeping the excellent separation performance of CMP membranes.

Boosting Drug Discovery for Parkinson's: Enhancement of the Delivery of a Monoamine Oxidase-B Inhibitor by Brain-Targeted PEGylated Polycaprolactone-Based Nanoparticles

The current pharmacological treatments for Parkinson's disease only offer symptomatic relief to the patients and are based on the administration of levodopa and catechol-O-methyltransferase or monoamine oxidase-B inhibitors (IMAO-B). Since the majority of drug candidates fail in pre- and clinical trials, due largely to bioavailability pitfalls, the use of polymeric nanoparticles (NPs) as drug delivery systems has been reported as an interesting tool to increase the stealth capacity of drugs or help drug candidates to surpass biological barriers, among other benefits. Thus, a novel potent, selective, and reversible IMAO-B (chromone C27, IC50 = 670 ± 130 pM) was encapsulated in poly(caprolactone) (PCL) NPs by a nanoprecipitation process. The resulting C27-loaded PEGylated PCL NPs (~213 nm) showed high stability and no cytotoxic effects in neuronal (SH-SY5Y), epithelial (Caco-2), and endothelial (hCMEC/D3) cells. An accumulation of PEGylated PCL NPs in the cytoplasm of SH-SY5Y and hCMEC/D3 cells was also observed, and their permeation across Caco-2 and hCMEC/D3 cell monolayers, used as in vitro models of the human intestine and blood-brain barrier, respectively, was demonstrated. PEGylated PCL NPs delivered C27 at concentrations higher than the MAO-B IC50 value, which provides evidence of their relevance to solving the drug discovery pitfalls.

Porous Polymers as Multifunctional Material Platforms toward Task-Specific Applications

Exploring advanced porous materials is of critical importance in the development of science and technology. Porous polymers, being famous for their all-organic components, tailored pore structures, and adjustable chemical components, have attracted an increasing level of research interest in a large number of applications, including gas adsorption/storage, separation, catalysis, environmental remediation, energy, optoelectronics, and health. Recent years have witnessed tremendous research breakthroughs in these fields thanks to the unique pore structures and versatile skeletons of porous polymers. Here, recent milestones in the diverse applications of porous polymers are presented, with an emphasis on the structural requirements or parameters that dominate their properties and functionalities. The Review covers the following applications: i) gas adsorption, ii) water treatment, iii) separation, iv) heterogeneous catalysis, v) electrochemical energy storage, vi) precursors for porous carbons, and vii) other applications (e.g., intelligent temperature control textiles, sensing, proton conduction, biomedicine, optoelectronics, and actuators). The key requirements for each application are discussed and an in-depth understanding of the structure-property relationships of these advanced materials is provided. Finally, a perspective on the future research directions and challenges in this field is presented for further studies.

Targeted Construction of Light-Harvesting Metal-Organic Frameworks Featuring Efficient Host-Guest Energy Transfer

Metal-organic frameworks (MOFs) have emerged as promising light-harvesting platforms for energy-transfer materials. However, the targeted construction of MOFs with desirable photophysical properties and pore structures is still a challenge. Herein, 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethene (tppe) is selected as the ligand for the construction of light-harvesting MOFs due to its highly emissive and rigid backbone, which could benefit the light-harvesting performance of the MOFs. Three MOFs (MOFs 1-3) were obtained on the basis of different metal centers (Zn²⁺ and Cd²⁺) and carboxylate building blocks. The complete structure characterization of the MOFs helps the illustration of the principles for structure tuning of this system. All three MOFs exhibit strong tppe-originated photoluminescence emission, with quantum yields as high as 47.6%. The fluorescence quantum yield and time-resolved fluorescence studies reveal that a remarkable energy-transfer efficiency (up to 96%) was achieved in this system. These results clearly indicate tppe-MOFs could be promising light-harvesting materials.

Cascade energy transfer and tunable emission from nanosheet hybrids: locating acceptor molecules through chiral doping

A donor–acceptor–donor triad with excellent intramolecular energy transfer (99%) exhibits cascade energy transfer in the presence of second acceptors leading to tunable emission colours. Chiral acceptor doping enables chiral induction and to locate acceptors in the donor scaffold.

Robust synthesis of free-standing and thickness controllable conjugated microporous polymer nanofilms

A new polymerization strategy based on Sonogashira–Hagihara reaction and Schiff-base reaction at oil–water interfaces is developed to synthesize free-standing and thickness controllable conjugated microporous polymer (CMP) nanofilms.

In situ synthesis of electroactive conjugated microporous fullerene films capable of supercapacitive energy storage

We describe a general strategy for synthesizing conjugated microporous fullerene thin films via a high-throughput, efficient and controllable thiophene-based electropolymerization.

Luminescent Porous Polymers Based on Aggregation-Induced Mechanism: Design, Synthesis and Functions

Enormous research efforts are focusing on the design and synthesis of advanced luminescent systems, owing to their diverse capability in scientific studies and technological developments. In particular, fluorescence systems based on aggregation-induced emission (AIE) have emerged to show great potential for sensing, bio-imaging, and optoelectronic applications. Among them, integrating AIE mechanisms to design porous polymers is unique because it enables the combination of porosity and luminescence activity in one molecular skeleton for functional design. In recent years rapid progress in exploring AIE-based porous polymers has developed a new class of luminescent materials that exhibit broad structural diversity, outstanding properties and functions and promising applications. By classifying the structural nature of the skeleton, herein the design principle, synthetic development and structural features of different porous luminescent materials are elucidated, including crystalline covalent organic frameworks (COFs), metal-organic frameworks (MOFs), and amorphous porous organic polymers (POPs). The functional exploration of these luminescent porous polymers are highlighted by emphasizing electronic interplay within the confined nanospace, fundamental issues to be addressed are disclosed, and future directions from chemistry, physics and materials science perspectives are proposed.

Highly sensitive gas-phase explosive detection by luminescent microporous polymer networks

We propose microporous networks (MPNs) of a light emitting spiro-carbazole based polymer (PSpCz) as luminescent sensor for nitro-aromatic compounds. The MPNs used in this study can be easily synthesized on arbitrarily sized/shaped substrates by simple and low-cost electrochemical deposition. The resulting MPN afford an extremely high specific surface area of 1300 m²/g, more than three orders of magnitude higher than that of the thin films of the respective monomer. We demonstrate, that the luminescence of PSpCz is selectively quenched by nitro-aromatic analytes, e.g. nitrobenzene, 2,4-DNT and TNT. In striking contrast to a control sample based on non-porous spiro-carbazole, which does not show any luminescence quenching upon exposure to TNT at levels of 3 ppm and below, the microporous PSpCz shows a clearly detectable response even at TNT concentrations as low as 5 ppb, clearly demonstrating the advantage of microporous films as luminescent sensors for traces of explosive analytes. This level states the vapor pressure of TNT at room temperature.

Design of Highly Photofunctional Porous Polymer Films with Controlled Thickness and Prominent Microporosity

Porous organic polymers allow the integration of various π-units into robust porous π-networks, but they are usually synthesized as unprocessable solids with poor light-emitting performance as a result of aggregation-related excitation dissipation. Herein, we report a general strategy for the synthesis of highly emissive photofunctional porous polymer films on the basis of a complementary scheme for the structural design of aggregation-induced-emissive π-systems. We developed a high-throughput and facile method for the direct synthesis of large-area porous thin films at the liquid-electrode interface. The approach enables the preparation of microporous films within only a few seconds or minutes and allows precise control over their thickness with sub-nanometer precision. By virtue of rapid photoinduced electron transfer, the thin films can detect explosives with enhanced sensitivity to low parts-per-million levels in a selective manner.