Spirobifluorene-BINOL-based microporous polymer nanoreactor for efficient 1H-tetrazole synthesis and iodine adsorption with facile charge transfer

Porous polymeric nanoreactors capable of multitasking are attractive and require a judicious design strategy. Herein, we describe an unusual approach for the synthesis of a porous polymer SBF-BINOL-6 by in situ formation of the BINOL entity taking substituted naphthols and spirobifluorene as co-monomers with high yield (81%). The as-synthesized polymer exhibited nanotube and nanosphere-like morphology, thermal endurance up to 372 °C and a BET surface area as high as 590 m2 g-1. The polymer endowed efficient loading of silver nanoparticles to generate Ag@SBF6, as confirmed from X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. Ag@SBF6 was effectively used as a heterogeneous catalyst towards the [3 + 2] dipolar cycloaddition reaction for the synthesis of biologically important 5-substituted 1H-tetrazoles with yields in the range of 75-99% and recyclability for at least seven times without a significant decline in its catalytic efficiency. Additionally, a superior host-guest interaction by the polymer offered iodine adsorption in the vapour phase with a high uptake capacity of up to 4.0 g g-1. Interestingly, the iodine-loaded polymer, I2@SBF6, demonstrated iodine-promoted increased conductivity (1.3 × 10-3 S cm-1) through facile charge transfer interactions.

Facile synthesis of MOF-derived N doped ZnO/C nanoparticles and its adsorption activity toward dye removal

Metal-organic framework (MOF)-derived materials have gained an increasing interest and showed potential adsorption features in numerous applications. Significant attempts have been performed to boost the structure, functionality, surface area and porosity in addition to adsorption performance of MOF-derived carbon nanoparticles. Here, nitrogen-doped ZnO/carbon nanoparticles were synthesized by directly pyrolysis of Zn based metal organic framework (ZIF-8) in a nitrogen atmosphere at two different temperatures (600 and 800 °C), followed by chemical impregnation with ZnCl2 solution with ratio (10:1) wt/wt, and thermal activation at 500 °C for 1 h. SEM, TEM, XPS, nitrogen adsorption-desorption method, and TGA characterization techniques were employed to investigate the morphology and structure characteristics. Then, thorough analysis of N doped ZnO/C-(600 and 800), adsorption capacity to remove Remazol brilliant blue reactive (RBBR) dye from aqueous phase was conducted. At room temperature, the porous N doped ZnO/C with high surface area attained a maximum adsorption capacity about 49.3 mg/g and demonstrated a strong adsorption capacity toward RBBR dye. The insights of kinetic, thermodynamic and adsorption isotherm studies of the as-demonstrated samples open up more discussion for MOFs-derived carbon adsorbents for wastewater treatment.

Mesoporous Porphyrin-Silica Nanocomposite as Solid Acid Catalyst for High Yield Synthesis of HMF in Water

Solid acid catalysts occupy a special class in heterogeneous catalysis for their efficiency in eco-friendly conversion of biomass into demanding chemicals. We synthesized porphyrin containing porous organic polymers (PorPOPs) using colloidal silica as a support. Post-modification with chlorosulfonic acid enabled sulfonic acid functionalization, and the resulting material (PorPOPS) showed excellent activity and durability for the conversion of fructose to 5-hydroxymethyl furfural (HMF) in green solvent water. PorPOPS composite was characterized by N2 sorption, FTIR, TGA, CHNS, FESEM, TEM and XPS techniques, justifying the successful synthesis of organic networks and the grafting of sulfonic acid sites (5 wt%). Furthermore, a high surface area (260 m2/g) and the presence of distinct mesopores of ~15 nm were distinctly different from the porphyrin containing sulfonated porous organic polymer (FePOP-1S). Surprisingly the hybrid PorPOPS showed an excellent yield of HMF (85%) and high selectivity (>90%) in water as compared to microporous pristine-FePOP-1S (yield of HMF = 35%). This research demonstrates the requirement of organic modification on silica surfaces to tailor the activity and selectivity of the catalysts. We foresee that this research may inspire further applications of biomass conversion in water in future environmental research.

CO2 hydrogenation over functional nanoporous polymers and metal-organic frameworks

CO₂ is one of the major environmental pollutants and its mitigation is attracting huge attention over the years due to continuous increase in this greenhouse gas emission in the atmosphere. Being environmentally hazardous and plentiful presence in nature, CO₂ utilization as C1 resource into fuels and feedstock is very demanding from the green chemistry perspectives. To accomplish this CO₂ utilization issue, functional organic materials like porous organic polymers (POPs), covalent organic frameworks (COFs) as well as organic-inorganic hybrid materials like metal-organic frameworks (MOFs), having characteristics of large surface area, high thermal stability and tunability in the porous nanostructures play significant role in designing the suitable catalyst for the CO₂ hydrogenation reactions. Although CO₂ hydrogenation is a widely studied and emerging area of research, till date review exclusively focused on designing POPs, COFs and MOFs bearing reactive functional groups is very limited. A thorough literature review on this matter will enrich our knowledge over the CO₂ hydrogenation processes and the catalytic sites responsible for carrying out these chemical transformations. We emphasize recent state-of-the art developments in POPs/COFs/MOFs having unique functionalities and topologies in stabilizing metallic NPs and molecular complexes for the CO₂ reduction reactions. The major differences between MOFs and porous organics are critically summarized in the outlook section with the aim of the future benefit in mitigating CO₂ emission from ambient air.

Adamantane-Based Micro- and Ultra-Microporous Frameworks for Efficient Small Gas and Toxic Organic Vapor Adsorption

Microporous organic polymers and related porous materials have been applied in a wide range of practical applications such as adsorption, catalysis, adsorption, and sensing fields. However, some limitations, like wide pore size distribution, may limit their further applications, especially for adsorption. Here, micro- and ultra-microporous frameworks (HBPBA-D and TBBPA-D) were designed and synthesized via Sonogashira–Hagihara coupling of six/eight-arm bromophenyl adamantane-based “knots” and alkynes-type “rod” monomers. The BET surface area and pore size distribution of these frameworks were in the region of 395–488 m² g⁻¹, 0.9–1.1 and 0.42 nm, respectively. The as-made prepared frameworks also showed good chemical ability and high thermal stability up to 350 °C, and at 800 °C only 30% mass loss was observed. Their adsorption capacities for small gas molecules such as CO₂ and CH₄ was 8.9–9.0 wt % and 1.43–1.63 wt % at 273 K/1 bar, and for the toxic organic vapors n-hexane and benzene, 104–172 mg g⁻¹ and 144–272 mg g⁻¹ at 298 K/0.8 bar, respectively. These are comparable to many porous polymers with higher BET specific surface areas or after functionalization. These properties make the resulting frameworks efficient absorbent alternatives for small gas or toxic vapor capture, especially in harsh environments.

Thiophene containing microporous and mesoporous nanoplates for separation of mercury from aqueous solution

Thiophene-based novel porous polymeric nanoplates synthesized through a template free approach show high mercury capture efficiency from contaminated water and may be promising for environmental applications.

Building metal-functionalized porous carbons from microporous organic polymers for CO2 capture and conversion under ambient conditions

Metal-functionalized porous carbons derived from microporous organic polymers remain highly desired for their intriguing physical and chemical properties.

Microporous Nanotubes and Nanospheres with Iron-Catechol Sites: Efficient Lewis Acid Catalyst and Support for Ag Nanoparticles in CO2 Fixation Reaction

Fe^III -containing hyper-crosslinked microporous nanotubes (FeNTs) and nanospheres (FeNSs) are synthesized through the reaction of catechol and dimethoxymethane in the presence of FeCl₃ or CF₃ SO₃ H. Both FeNTs and FeNSs demonstrate excellent catalytic activity in Lewis acid catalysis (hydrolysis and regioselective methanolysis of styrene oxide) and tandem catalysis involving a sequential oxidation-cyclization process, which selectively converts benzyl alcohol to 2-phenyl benzimidazole. Apart from Lewis acidity, the FeNTs and FeNSs also showed CO₂ uptake capacities of 2.6 and 2.2 mmol g^-1 , respectively, at a pressure of 1 atm and temperature of 273 K. Furthermore, Ag nanoparticles are immobilized successfully on the surfaces of FeNTs and FeNSs by the liquid-phase impregnation method to prepare Ag@FeNT and Ag@FeNS nanocomposites, which show high catalytic activity for the selective fixation of CO₂ to phenylacetylene to yield phenylpropiolic acid at 60 °C and 1 atm CO₂ pressure. Hence, Fe^III -catechol-containing hyper-crosslinked nanotubes and nanospheres have huge potential not only as Lewis acid catalysts, but also as excellent supports for immobilizing Ag nanoparticles in the design of a robust catalyst for the carboxylation of terminal alkynes, which has wide scope in catalysis and environmental research.

Facile Synthesis of a Pentiptycene-Based Highly Microporous Organic Polymer for Gas Storage and Water Treatment

Rigid H-shaped pentiptycene units, with an intrinsic hierarchical structure, were employed to fabricate a highly microporous organic polymer sorbent via Friedel-Crafts reaction/polymerization. The obtained microporous polymer exhibits good thermal stability, a high Brunauer-Emmett-Teller surface area of 1604 m² g^-1, outstanding CO₂, H₂, and CH₄ storage capacities, as well as good adsorption selectivities for the separation of CO₂/N₂ and CO₂/CH₄ gas pairs. The CO₂ uptake values reached as high as 5.00 mmol g^-1 (1.0 bar and 273 K), which, along with high adsorption selectivity values (e.g., 47.1 for CO₂/N₂), make the pentiptycene-based microporous organic polymer (PMOP) a promising sorbent material for carbon capture from flue gas and natural gas purification. Moreover, the PMOP material displayed superior absorption capacities for organic solvents and dyes. For example, the maximum adsorption capacities for methylene blue and Congo red were 394 and 932 mg g^-1, respectively, promoting the potential of the PMOP as an excellent sorbent for environmental remediation and water treatment.

Hypercrosslinked porous polymer materials: design, synthesis, and applications

Hypercrosslinked polymers (HCPs) are a series of permanent microporous polymer materials initially reported by Davankov, and have received an increasing level of research interest. In recent years, HCPs have experienced rapid growth due to their remarkable advantages such as diverse synthetic methods, easy functionalization, high surface area, low cost reagents and mild operating conditions. Judicious selection of monomers, appropriate length crosslinkers and optimized reaction conditions yielded a well-developed polymer framework with an adjusted porous topology. Post fabrication of the as developed network facilitates the incorporation of various chemical functionalities that may lead to interesting properties and enhance the selection toward a specific application. To date, numerous HCPs have been prepared by post-crosslinking polystyrene-based precursors, one-step self-polycondensation or external crosslinking strategies. The advent of these methodologies has prompted researchers to construct well-defined porous polymer networks with customized micromorphology and functionalities. In this review, we describe not only the basic synthetic principles and strategies of HCPs, but also the advancements in the structural and morphological study as well as the frontiers of potential applications in energy and environmental fields such as gas storage, carbon capture, removal of pollutants, molecular separation, catalysis, drug delivery, sensing etc.

Rational skeletal rigidity of conjugated microporous polythiophenes for gas uptake

A step by step increase of the skeleton rigidity of the polythiophene networks P-TTT, P-THIDT and P-DTBDT by monomer design. The monomers’ rigidity had intense influence on the stacking morphology and porosity structure of the obtained polythiophenes.