The short review discusses a family of amorphous porous organic polymers, conjugated microporous polymer (CMP), which is distinctive in fusion of a large π-electronic conjugation within the topological network platform. The kind of polymers has shown the synthetic variety, the advanced capability and the wide applicability in contrast to the reported analogues. Herein, the significant progress of CMP applications has been summarized to showcase their capability in constructing photo-functional systems.The mini review emphasizes on the recent application progress of photo-functional conjugated microporous polymers in energy, environmental and biomedical fields.Download high-res image (152KB)Download full-size image

A hydrid microsphere Fe3O4@carbon@poly(InIII-carboxylate) consisting of a cluster of Fe3O4 nanoparticles as the core, a carbon layer as the inner shell and a porous InIII–carboxylate coordination polymer as the outer shell was prepared and applied as a recyclable catalyst for the cycloaddition reaction of CO2 and epoxides. Construction of this hybrid microsphere was achieved in the two steps, including (1) the one-pot solvothermal synthesis of Fe3O4@C particles with the abundant carboxylic groups on the carbon surface and (2) the subsequent growth of the outer shell polymers based on the precipitation coordination polymerization. Imidazolium-substituted Salen ligands were synthesized and chelated with the In(III) ions using the terminal carboxylic groups. The coordination polymer shell was formed on the Fe3O4@C particles, and the structures including shell thickness, surface area and porosity could be varied by tuning the feeding ratios of the In(III) ions and the ligands. The optimal structure of the coordination polymers showed a shell thickness of ca. 45 nm with ∼5 nm of mesopore, 174.7 m2/g of surface area and 0.2175 cm3/g of pore volume. In light of gas uptake capability, catalytic activity and magnetic susceptibility, cycloaddition of CO2 with a series of epoxides were studied by using Al-complexed Fe3O4@C@InIII-[IL-Salen] microspheres. The results validated that the self-supporting catalytic layer with high surface area was of remarkable advantages, which were attributed from great increment of effective active sites and combination of nucleophilic/electrophilic synergistic property and CO2 uptake capability. Therefore, these hybrid microspheres provided excellent catalytic activity, prominent selectivity to cyclic carbonates and outstanding recyclability with the assistance of an applied magnetic field.Keywords: bifunctional catalysts; CO2; coordination polymers; cycloaddition; magnetic nanoparticles

The one-step synthesis of nanoscale conjugated microporous polymer (NCMP) capsules is presented by using PMAA microspheres as self-sacrificial templates. Precise control over the morphology, nanostructure and shell thickness makes the NCMPs have a tunable NIR absorption ability and a shape-dependent photothermal conversion efficiency. Upon exposure to 808 nm light, they rapidly generate heat (NCMP concentration: 100 μg mL−1) and cause thermal ablation of HeLa cells with less than 10% viability.

We present the preparation of nanoscale porous organic polymer (POP) composite microspheres consisting of an Fe3O4 supraparticle as the core and micro-/mesoporous POP as the shell. The core/shell-structured Fe3O4@PS microspheres were synthesized, and then subjected to a seeded swelling polymerization in the PS shell using a mixture of divinyl benzene (DVB) and vinylbenzene chloride (VBC). The formed poly(VBC-co-DVB) networks were blended with PS in the shell, resulting in a distinct phase segregation. Upon a Friedel–Craft-type hyper-crosslinking treatment, the POP structure was obtained showing the specific porosity. During this process, the non-crosslinking PS chains were extracted out of the shell and large-sized mesopores were achieved with the micropores obtained by the hyper-crosslinking networks. By varying the feed amount of VBC and DVB, the phase segregation was changed and the prevailing mesopores could be tuned from 4 nm to 30 nm. The contribution of micropores to the entire porosity was accordingly altered. In light of the characteristics of dual-level pores and magnetic recyclability, the Pt nanoparticles were locally reduced within the mesopores, and the reactive substrates were then accessible to microporous zones in the POP shell. The enantioselective hydrogenation of ethyl pyruvate was applied to evaluate the catalytic activity of the Fe3O4@POP/Pt composites. Under optimized conditions (20 bar H2 pressure, 20 h, R.T. and molar ratio of Pt/CD: 6/1), the Fe3O4@POP/Pt composite catalysts containing 10 wt% Pt nanoparticles were validated to have excellent catalytic activity, outstanding reusability, and a high product yield and ee value (80.7%) for the enantioselective conversion of ethyl pyruvate to ethyl lactate.

A Pd(II)/Cu(I) cocatalyzed homocoupling reaction of terminal alkynes to diynes was used to synthesize conjugated polymer organogels with tetragonal topological frameworks consisting of Zn-porphyrin units as nodes and diynes as struts. This material appears fibrous with a micrometer length, possesses outstanding elastic properties, and could be organized into desired modules. Upon drying, the transformed xerogels afford superior thermal stability and microporosity, implying that they are supported by conjugated microporous polymer (CMP) skeletons at the molecular level. The microporosity of CMP-structured xerogels could be adjusted by varying the monomer concentrations, reaction temperatures and solvent species. The notable narrowed pore size distribution is achieved under optimal conditions, which results in CMP-supported xerogels outperforming the most reported CMPs, although the networks are still amorphous in nature. By following the same synthesis route, for the first time, the interpenetrating polymer network organogels were prepared by forming two CMP components sequentially in a temperature-controlled manner and in one pot. This provides an unprecedented combination of multiple interwoven CMP modules whose functions could be assembled synergistically for prospective broader applications.

Metalloporphyrin-based CMP nanoparticles synthesized by the oxidative dimerization of terminal alkynes in the toluene-in-water miniemulsion possess native porosity, outstanding solution processability and uniform nanosized distribution. Also, they exhibit the sensitive color-switching ability for quantitative assay of gaseous SO2 by the noncovalent complex-displacement reaction at liquid–solid or gas–solid interfaces.

Rattle-type porous carbon microcapsules (RPCMs) were deliberately designed to combine multiple functions with the aim of improving the applicability of amorphous carbon in a synergistic fashion. A movable Fe3O4 nanocluster coated with porous carbon is encapsulated in the cavity of a carbon microcapsule with an eggshell-like characteristic, allowing for storage, adsorption, and exchange of matters through the mesoporous channels of the carbon layer. The synthetic strategy of RPCMs is flexible and universal, involving the constitution and carbonization of Fe3O4@PF@PS@PF template particles. This results in a double carbon shell and a sandwiched hollow cavity with a movable magnetic core. There is evidence that RPCMs possess large surface areas, hierarchical pore sizes, hydrophobicity, and magnetic responsiveness. Hence, diverse applications have been investigated. It is proved that RPCMs exhibit excellent performance in the effective enrichment of peptides/proteins. The detection limit toward peptides could reach as low as 10 nM, and the enrichment capacity toward MYO protein is as high as 410 mg/g (protein/beads). Furthermore, RPCMs are able to harvest proteins in complex real samples such as fetal bovine serum and rabbit blood. In addition, RPCMs could be fabricated in a supercapacitor electrode and display outstanding energy-storage performance. The electrochemical measurements demonstrate that RPCM-based electrodes have a specific capacitance of as high as 216 F/g (0.1 A/g), long-term cycling stability with a capacitance retention of 92.4% over 1000 cycles (0.2 A/g), and good electronic conductivity.Keywords: magnetic nanoparticles; peptides/proteins enrichment; porous carbon; rattle structure; supercapacitor

A two-step polymerization combining miniemulsion and solvothermal techniques was applied to synthesize tetraphenylethene-based nanoscale conjugated microporous polymers (TPE-NCMP), which simultaneously possessed a large surface area (1214 m2/g) and a high aggregation-induced florescence quantum yield (58%). Immobilization of Nile Red within micropores of TPE-NCMPs constructed a light-harvesting composite with characteristics of intense photons acquisition and efficient energy migration. Homogenous NCMP-based films were fabricated by blending the dye-doped TPE-NCMPs with PVA. The fluorescence emission could be flexibly tuned by varying the dosage of dyes over the whole visible spectrum including a pure white light.

An exquisitely structured CPP consisting of a self-supported POM-Zn(II) coordination polymer as the shell and a Fe3O4 cluster as the core was synthesized, which could be fabricated as a supercapacitive film electrode showing prominent electrochemical activities for enormous energy storage.

Ascorbic acid (AA) is capable of inhibiting cancer cell growth by perturbing the normal redox state of cells and causing toxic effects through the generation of abundant reactive-oxygen species (ROS). However, the clinical utility of AA at a tolerable dosage is plagued by a relatively low in vivo efficacy. This study describes the development of a peroxidase-like composite nanoparticle for use in an AA-mediated therapeutic strategy. On the basis of a high-throughput, one-pot solvothermal approach, Fe3O4@C nanoparticles (NPs) were synthesized and then modified with folic acid (FA) on the surface. Particular focus is concentrated on the assessment of peroxidase-like catalytic activity by a chromogenic reaction in the presence of H2O2. The carbon shell of Fe3O4@C NPs contains partially graphitized carbon and thus facilitates electron transfer in the catalytic decomposition of H2O2, leading to the production of highly reactive hydroxyl radicals. Along with magnetic responsiveness and receptor-binding specificity, the intrinsic peroxidase-like catalytic activity of Fe3O4@C-FA NPs pronouncedly promotes AA-induced oxidative stress in cancer cells and optimizes the ROS-mediated antineoplastic efficacy of exogenous AA. In vitro experiments using human prostate cancer PC-3 cells demonstrate that Fe3O4@C-FA NPs serve as a peroxidase mimic to create hydroxyl radicals from endogenous H2O2 that is yielded in response to exogenous AA via an oxidative stress process. The usage of a dual agent leads to the enhanced cytotoxicity of PC-3 cells, and, because of the synergistic effect of NPs, the administrated dosage of AA is reduced markedly. However, because normal cells (HEK 293T cells) appear to have a higher capacity to cope with additionally generated ROS than cancer cells, the NP–AA combination shows little damage in this case, proving that selective killing of cancer cells could be achieved owing to preferential accumulation of ROS in cancer cells. A possible ROS-mediated mechanism is discussed to elucidate the pharmaceutical profile of the NP–AA agent. In general, this foundational study reveals that the peroxidase-like nanomaterials are applicable for modulating oxidative stress for the selective treatment of cancer cells by generating a high level of endogenous ROS.Keywords: ascorbic acid; magnetic nanoparticles; peroxidase; reactive oxygen species; synergistic effect; target drug delivery;

A novel multifunctional conjugated nanoporous polymer colloid (CNPC) combined with metal nanocrystals has been synthesized using the Sonogashira coupling reaction in a toluene-in-water miniemulsion. It is composed of a poly(phenylene ethynylene) (PPE) network that is covalently inlaid with the locked-in Fe3O4 nanocrystals. The Fe3O4@CNPC has a narrowly distributed size and uniform morphology, preserves the advanced porosity and fluorescence emission of the conjugated polymer network, and shows rapid magnetic response and high catalytic activity. The magnetic content can be controlled during the synthesis. This is accompanied by a corresponding enhancement of the size and surface area of the mesopores. In view of those characteristics, Fe3O4@CNPC is able to behave as fluorescence sensor for the detection of phenolic compounds. Acetaminophen (APAP) has been used as a model compound and the test results demonstrate that the Fe3O4-catalyzed oxidation of APAP takes place within the pores of the PPE network in the presence of H2O2. The oxidized intermediates are reactive radicals and can remove electrons from the π-conjugated PPE network, eventually leading to a decrease or even quenching of its fluorescence. Since the multiple functions of Fe3O4@CNPC fully cooperate, it produces a rapid optical response and superior sensitivity for the detection of APAP at micromolar concentrations.

Typical biopolymers, including soybean, casein, γ-poly(glutamic acid) (PGA), agarose and chitosan, were investigated as stabilizers in the synthesis of nanoporous magnetite colloidal nanocrystal clusters (MCNCs) by the hydrolysis and reduction of iron(III) chloride hydrate in ethylene glycol at 200 °C. The cluster sizes, morphologies, porous structures and magnetization of the resulting MCNCs were significantly affected by the different biopolymers. Of those members, soybean protein enabled the formation of spongy MCNCs with a surprisingly high specific surface area of 207 m2 g−1 and a characteristic mesopore diameter of 6.3 nm. Use of the other biopolymers (e.g. PGA and casein) led to the formation of MCNCs with lower specific surface areas (>100 m2 g−1) but considerably enhanced saturation magnetizations (∼60 emu g−1). Our results further shed light on the role played by the biopolymers in the structural evolution of the porous nanocrystal clusters. Analysis by characterizations of TEM and TGA showed that the decomposition of the biopolymer chains may have occurred during the transition from solid to porous clusters. As such, it is most likely that the biopolymers including soybean, casein and PGA serve as sacrificial templates to direct the formation of high-surface-area MCNCs. Taking into account the comprehensive properties of the different MCNCs, the PGA-stabilized MCNCs were selected as a drug delivery vehicle to simultaneously encapsulate therapeutic docetaxel (DOC) and ceramide (CER) via the hydrogen bonding interaction, for the treatment of prostate cancer. The inhibitory and apoptotic effects of the loaded DOC and CER co-delivered within MCNCs were evaluated in the prostate cancer cell line (PC-3) in vitro.

The heterostructure Ag–Au bimetallic nanocrystals supported on Fe3O4@carbon composite microspheres were synthesized by one facile and controllable approach, wherein the Ag nanocrystals attached on the Fe3O4@carbon microspheres were prepared first and served as reductant for the galvanic replacement reaction with the Au precursor (HAuCl4). Upon varying the feeding amounts of the Au precursor, the bimetallic compositions on the Fe3O4@carbon microsphere could be readily tuned resulting in a series of composite microspheres with different Au-to-Ag molar ratios. Subsequently, we thus investigated the catalytic activity and selectivity of the magnetic composite catalysts from two sides. First, 4-nitrophenol (4-NP) was applied as a model molecule to study the effect of different Au-to-Ag molar ratios on catalytic capabilities of the resulting composite microspheres. It was found that upon the addition of NaBH4 the catalytic capability was markedly enhanced when the Au content was increased. The maximum activity parameter value reached 1580 s–1 g–1, which is far higher than those of known monometallic composites. Also, they could give the equally high yields for other nitroaromatic compounds with various substituents, irrespective of the linked electron-donating or electron-withdrawing groups. Second, the synergistic effects of the carbon substrate in the catalysis reaction were demonstrated. When compared with colloidal SiO2, TiO2, and poly(styrene-co-acrylic acid) substrates, the carbon support not only facilitated the enhancement of the catalytic performance of the noble metal nanocrystals but was also more suitable for the in situ preparation of Au–Ag bimetallic nanocrystals using the GRR. Besides, the particles’ convenience in terms of their magnetic separability and outstanding reusability was validated through many successive reduction reaction cycles. In light of these unique characteristics, the Fe3O4@C@Ag–Au composite microspheres show promising and great potential for practical applications.

Conjugated nanoporous polymer colloids (CNPCs) consisting of covalently cross-linked poly(p-phenyleneethynylene) networks were synthesized by using the Sonogashira coupling reaction in a toluene-in-water miniemulsion. The synthesized CNPCs having a uniform particle size distribution exhibit high porosity with a specific surface area of 421 m2/g and a dual distribution of pore size in the micropore and mesopore ranges. They are amenable to postfunctionalization and enhancement of their dispersibility in solvents, and retain their native photoluminescence. The modified CNPCs allow for in situ incorporation of palladium nanocrystals to form the Pd@CNPC composite materials. The Pd@CNPCs are validated to have excellent catalytic activity, outstanding reusability, and exceptionally high TOF (44100 h–1) for the Suzuki–Miyaura coupling reaction.Keywords: composite colloids; conjugated polymer networks; heterogeneous catalysis; nanoporosity; Pd nanocrystals;

A novel multifunctional conjugated nanoporous polymer colloid (CNPC) combined with metal nanocrystals has been synthesized using the Sonogashira coupling reaction in a toluene-in-water miniemulsion. It is composed of a poly(phenylene ethynylene) (PPE) network that is covalently inlaid with the locked-in Fe3O4 nanocrystals. The Fe3O4@CNPC has a narrowly distributed size and uniform morphology, preserves the advanced porosity and fluorescence emission of the conjugated polymer network, and shows rapid magnetic response and high catalytic activity. The magnetic content can be controlled during the synthesis. This is accompanied by a corresponding enhancement of the size and surface area of the mesopores. In view of those characteristics, Fe3O4@CNPC is able to behave as fluorescence sensor for the detection of phenolic compounds. Acetaminophen (APAP) has been used as a model compound and the test results demonstrate that the Fe3O4-catalyzed oxidation of APAP takes place within the pores of the PPE network in the presence of H2O2. The oxidized intermediates are reactive radicals and can remove electrons from the π-conjugated PPE network, eventually leading to a decrease or even quenching of its fluorescence. Since the multiple functions of Fe3O4@CNPC fully cooperate, it produces a rapid optical response and superior sensitivity for the detection of APAP at micromolar concentrations.

Typical biopolymers, including soybean, casein, γ-poly(glutamic acid) (PGA), agarose and chitosan, were investigated as stabilizers in the synthesis of nanoporous magnetite colloidal nanocrystal clusters (MCNCs) by the hydrolysis and reduction of iron(III) chloride hydrate in ethylene glycol at 200 °C. The cluster sizes, morphologies, porous structures and magnetization of the resulting MCNCs were significantly affected by the different biopolymers. Of those members, soybean protein enabled the formation of spongy MCNCs with a surprisingly high specific surface area of 207 m2 g−1 and a characteristic mesopore diameter of 6.3 nm. Use of the other biopolymers (e.g. PGA and casein) led to the formation of MCNCs with lower specific surface areas (>100 m2 g−1) but considerably enhanced saturation magnetizations (∼60 emu g−1). Our results further shed light on the role played by the biopolymers in the structural evolution of the porous nanocrystal clusters. Analysis by characterizations of TEM and TGA showed that the decomposition of the biopolymer chains may have occurred during the transition from solid to porous clusters. As such, it is most likely that the biopolymers including soybean, casein and PGA serve as sacrificial templates to direct the formation of high-surface-area MCNCs. Taking into account the comprehensive properties of the different MCNCs, the PGA-stabilized MCNCs were selected as a drug delivery vehicle to simultaneously encapsulate therapeutic docetaxel (DOC) and ceramide (CER) via the hydrogen bonding interaction, for the treatment of prostate cancer. The inhibitory and apoptotic effects of the loaded DOC and CER co-delivered within MCNCs were evaluated in the prostate cancer cell line (PC-3) in vitro.

An exquisitely structured CPP consisting of a self-supported POM-Zn(II) coordination polymer as the shell and a Fe3O4 cluster as the core was synthesized, which could be fabricated as a supercapacitive film electrode showing prominent electrochemical activities for enormous energy storage.

Metalloporphyrin-based CMP nanoparticles synthesized by the oxidative dimerization of terminal alkynes in the toluene-in-water miniemulsion possess native porosity, outstanding solution processability and uniform nanosized distribution. Also, they exhibit the sensitive color-switching ability for quantitative assay of gaseous SO2 by the noncovalent complex-displacement reaction at liquid–solid or gas–solid interfaces.