Probing the Effects of Templating on the UV and Visible Light Photocatalytic Activity of Porous Nitrogen-Modified Titania Monoliths for Dye Removal

Crystalline organic monoliths with bicontinuous porosity

Organic crystals are a promising class of materials for various optical applications. However, it has been challenging to make macroscopic organic crystals with bicontinuous porosity that are applicable to flow chemistry. In this study, a new class of porous materials, cm-scale crystalline organic monoliths (COMs) with bicontinuous porosity, are synthesized by replicating the porous structure of silica monolith templates. The COMs composed of p-terphenyl can take up more than 30 wt% of an aqueous solution, and the photophysical properties of the p-terphenyl crystals are well maintained in the COMs. The relatively high surface area of the COMs can be exploited for efficient Dexter energy transfer from triplet sensitizers on the pore surface. The resulting triplet excitons in the COMs encounter and annihilate, generating upconverted UV emission. The COMs would open a new avenue toward applications of organic crystals in flow photoreaction systems.

Sustainable green conversion of coal gangue waste into cost-effective porous multimetallic silicate adsorbent enables superefficient removal of Cd(II) and dye

Converting solid wastes into new materials for wastewater decontamination is a feasible "one stone, three birds" strategy to achieve sustainable value-added utilization of resources and minimize waste emissions, but significant challenges remain. In response to this, we proposed an efficient "mineral gene reconstruction" method to synchronously transform coal gangue (CG) into a green porous silicate adsorbent without using any harmful chemicals (i.e., surfactants, organic solvents). The one of the synthesized adsorbents with a high specific surface area (582.28 m²/g) and multimetallic active centres shows outstanding adsorption performance (adsorption capacities: 168.92 mg/g for Cd(II), 234.19 mg/g for methylene blue (MB); removal rate: 99.04% for Cd(II) and 99.9% for MB). The adsorbent can also reach a high removal rate of 99.05%∼99.46% and 89.23%∼99.32% for MB and Cd(II) in real water samples (i.e., Yangtze River, Yellow River, seawater and tap water), respectively. After 5 adsorption-desorption cycles, the adsorption efficiency remained above 90%. The adsorbents mainly adsorbed Cd(II) by electrostatic attraction, surface complexation and partial ion exchange and MB by electrostatic and hydrogen bonding interactions. This study provides a sustainable and promising platform for developing a new-generation cost-efficient adsorbent from waste for clean water production.

Design, Manufacturing and Functions of Pore-Structured Materials: From Biomimetics to Artificial

Porous structures with light weight and high mechanical performance exist widely in the tissues of animals and plants. Biomimetic materials with those porous structures have been well-developed, and their highly specific surfaces can be further used in functional integration. However, most porous structures in those tissues can hardly be entirely duplicated, and their complex structure-performance relationship may still be not fully understood. The key challenges in promoting the applications of biomimetic porous materials are to figure out the essential factors in hierarchical porous structures and to develop matched preparation methods to control those factors precisely. Hence, this article reviews the existing methods to prepare biomimetic porous structures. Then, the well-proved effects of micropores, mesopores, and macropores on their various properties are introduced, including mechanical, electric, magnetic, thermotics, acoustic, and chemical properties. The advantages and disadvantages of hierarchical porous structures and their preparation methods are deeply evaluated. Focusing on those disadvantages and aiming to improve the performance and functions, we summarize several modification strategies and discuss the possibility of replacing biomimetic porous structures with meta-structures.

Novel alginate immobilized TiO2 reusable functional hydrogel beads with high photocatalytic removal of dye pollutions

TiO2 semiconductor photocatalysis is an effective technology for the treatment of wastewater containing organic dye pollutants, which has been received extensive focus. However, the problems in the recovery and reutilization process impede the large-scale applications of particulate photocatalytic materials. Herein, a macro sized hydrogel bead loaded with nano TiO2 powder was successfully prepared by taking advantage of the cross-linking and gel property of alginate salt, which could form egg-box structure naturally when Na+ ions in sodium alginate (SA) were replaced by divalent ions such as Cu2+, Co2+, and Sr2+ ions. The photocatalytic degradation rate of methyl orange (MO) solution in the presence of the hydrogel beads reaches 99% within 60 min under the ultraviolet light irradiation, which is competitive with that of TiO2 nano powder. Furthermore, the hydrogel beads prepared by this strategy maintain over 95% photocatalytic degradation rate after 10 cycles of degradation process. The results indicate that the network structure of alginate could immobilize and disperse TiO2 particle effectively, and it is readily for the spherical beads to contact and harvest the light, making the alginate beads have excellent photocatalytic functions. Also, the alginate based beads integrate good performance with high stability and excellent recyclability perfectly.

Tailoring the defects of sub-100 nm multipodal titanium nitride/oxynitride nanotubes for efficient water splitting performance

Deciphering the photocatalytic-defect relationship of photoanodes can pave the way towards the rational design for high-performance solar energy conversion. Herein, we rationally designed uniform and aligned ultrathin sub-100 nm multipodal titanium nitride/oxynitride nanotubes (TiON _x NTs) (x = 2, 4, and 6 h) via the anodic oxidation of Ti-foil in a formamide-based electrolyte followed by annealing under ammonia gas for different durations. XPS, XPS imaging, Auger electron spectra, and positron annihilation spectroscopy disclosed that the high nitridation rate induced the generation of a mixture of Ti-nitride and oxynitride with various vacancy-type defects, including monovacancies, vacancy clusters, and a few voids inside TiO _x NTs. These defects decreased the bandgap energy to 2.4 eV, increased visible-light response, and enhanced the incident photon-to-current collection efficiency (IPCE) and the photocurrent density of TiON _x NTs by nearly 8 times compared with TiO₂NTs, besides a quick carrier diffusion at the nanotube/electrolyte interface. The water-splitting performance of sub-100 nm TiON₆NT multipodal nanotubes was superior to the long compacted TiON _x NTs with different lengths and TiO₂ nanoparticles. Thus, the optimization of the nitridation rate tailors the defect concentration, thereby achieving the highest solar conversion efficiency.

PVA/Pt/N-TiO2/SrTiO3 porous films with adjustable pore size for hydrogen production under simulated sunlight

In this study, poly(vinyl alcohol)/platinum/nitrogen-doped titanium dioxide/strontium titanate composite (PVA/Pt/NT/STO) porous films with adjustable pore sizes were successfully synthesized using the facile etching SiO₂ method. This enhanced the light transmittance and contact rate between the photocatalyst and solution. The effects of the size and number of the pores on the hydrogen production rate were studied under simulated sunlight. The pore size of the PVA/Pt/NT/STO film increased with increasing particle size of the as-prepared SiO₂, and the photocatalytic hydrogen production efficiency increased with increasing pore size and number. Due to the formation of pores on the film, the light transmittance and charge separation of the film increased. Owing to the good light transmittance and charge separation of the porous PVA/Pt/NT/STO film, the optimal photocatalytic hydrogen production rate of the PVA/Pt/NT/STO-8S-I-20 reached 34,895 μmol/h/g when the alcohol solvent, synthesis time, and SiO₂ concentration were isopropanol, 20 h, and 8 wt%, respectively. Furthermore, the photocatalytic hydrogen production rate was approximately three times higher than that of the dense PVA/Pt/NT/STO film.

Core–shell magnetic mesoporous N-doped silica nanoparticles: solid base catalysts for the preparation of some arylpyrimido[4,5-b]quinoline diones under green conditions

Nowadays, the application of solid base catalysts as a perfect replacement for homogenous basic catalysts has attracted the attention of researchers. In this study, core–shell magnetic mesoporous N-doped silica nanoparticles N(x wt%)-MSN, as a heterogeneous base catalyst, were synthesized. The N(x wt%)-MSN composite was fabricated by adding different amounts of diethanolamine as a source of nitrogen, besides using tetraethylorthosilicate as a precursor of silica. The as-prepared catalyst was employed efficiently for the synthesis of some arylpyrimido[4,5-b]quinoline-dione derivatives under green conditions. The highly efficient catalyst N(1.3 wt%)-MSN was characterized via XRD, FESEM, HRTEM, BET and XPS techniques, and the results of these analyses proved that the nitrogen was doped into the silica structure. Also, the results demonstrated the core–shell structure of the as-synthesized composite.

Preparation of core–shell magnetic mesoporous N-doped silica nanoparticles as a new solid base catalyst was studied. obtained catalyst was used for the preparation of some arylpyrimido[4,5-b]quinoline diones under green conditions.

Organic–inorganic bimetallic hybrid particles with controllable morphology for the catalytic degradation of organic dyes

Amphiphilic bimetallic hybrid Janus nanoparticles with controllable morphology and ability to perform highly efficient catalytic degradation of organic dyes.

Facile one-pot synthesis of a porphyrin-based hydrophilic porous organic polymer and application as recyclable absorbent for selective separation of methylene blue

With the development of dye production and printing industry, dyes wastewater has increased dramatically. The resulting environmental pollution problem is increasing seriously. In the present work, a porphyrin-based porous organic polymer (PPOPs-OH) was synthesized by using pyrrole and 2,6-dihydroxynaphthalene-1,5-dicarbaldehyde (DHNDA) as basic building block in situ. This method was cost- and time-efficient, without the participation of metal catalysts. Further reaction of PPOPs-OH with chlorosulfonic acid, a new sulfonic acid functional material (PPOPs-SO₃H) was obtained with the increasing electronegativity and hydrophilicity. PPOPs-SO₃H exhibit good adsorption capacity for methylene blue (MB) from water (980.4 mg g^-1) and excellent selectivity for MB in the present of rhodamine B (RhB) and methyl orange (MO). Mechanism investigation revealed that electrostatic in comparison with π-π interaction is the prominent force in the absorption process. Recycling experiments found the absorption properties of PPOPs-SO₃H did not reduce significantly after several cycles. As a consequence, our findings highlight an appealing opportunities for covalent organic polymers with their potential application as high-efficiency and robust adsorbents for pollutants removal and environmental protection.

Chitin/clay microspheres with hierarchical architecture for highly efficient removal of organic dyes

Numerous adsorbents have been reported for efficient removal of dye from water, but the high cost raw materials and complicated fabrication process limit their practical applications. Herein, novel nanocomposite microspheres were fabricated from chitin and clay by a simple thermally induced sol-gel transition. Clay nanosheets were uniformly embedded in a nanofiber weaved chitin microsphere matrix, leading to their hierarchical architecture. Benefiting from this unique structure, microspheres could efficiently remove methylene blue (MB) through a spontaneous physic-sorption process which fit well with pseudo-second-order and Langmuir isotherm models. The maximal values of adsorption capability obtained by calculation and experiment were 152.2 and 156.7 mg g^-1, respectively. Chitin/clay microspheres (CCM2) could remove 99.99% MB from its aqueous solution (10 mg g^-1) within 20 min. These findings provide insight into a new strategy for fabrication of dye adsorbents with hierarchical structure from low cost raw materials.

A study on the transfer of photo-excited charge carriers within direct and inverted type-I heterojunctions of CdS and ZnS QDs

Wave function engineering for fast charge carrier separation/slow recombination in reverse type-I core/shell QDs for solar photocatalysis.