Porous organic polymers

Porous organic polymers (POPs) are emerging porous materials, which have developed very quickly and drawn more and more attention. The new reactions and optimized reaction conditions resulted in the formation of ordered porous structures, more variety of applications, and more research groups contributing to this promising research field. It is the right time to have a special issue on POPs. I am glad to be the guest editor of this special issue in Journal of Polymer Science. There are 20 contributions in this issue, including four reviews and 16 research articles, ranging from hyper-crosslinked polymers (HCPs), CMPs, to COFs, and spanning from molecular capture and sensing to catalysis and energy storage. Owing to the microporosity and functional moieties inside the pores, POPs show promising capture performance of various ions/molecules. Shi et al. (pol.20230469) comprehensively summarized recent researches on the post-synthetic approaches and CO2 capture performances of amine-functionalized POPs. The structure–performance relationships, i.e. the impact of the amine type and density on the CO2 capture capacity, CO2/N2 selectivity, heat of adsorption, sorption kinetics, and recyclability, will help develop the practically promising adsorbents for CO2 especially with low partition pressures. Three research articles by Fu et al. (pol.20230269), Zhao et al. (pol.20230244), and Shi et al. (pol.20230258) prepared sulfhydryl-functionalized HCPs, POSS-based HCPs, and three-component covalent organic polymers (COPs), and investigated their capture behaviors of metal ions (Pd2+ and Ag+), neonicotinoid insecticides (imidacloprid, acetamidine, and thiamethoxam) and dyes (Congo red and Rhodamine B), and antibiotic (ciprofloxacin), respectively. Due to their conjugation and porosity, POPs display excellent sensing ability to different molecules. Liu et al. (pol.20220683) reviewed the progresses of COFs as analytic platforms with high specific surface area, great stability, and adjustable pore size. The structure adjustability and ease in functionalization of COFs endow them promising performance in electrochemical, photoelectrochemical, and colorimetric sensing of biomolecules, antibacterial drugs, and organic poisons, inorganic metal cations, drugs, pesticides, and biomarkers. In three research articles, Li et al. (pol.20230137), Chen et al. (pol.20220662), and Liu et al. (pol.20230150) reported the preparation of triphenylamine- and triazine-based conjugated microporous polymers, mesoporous polydopamine nanofilms, and imine-linked COFs with ester groups, and their sensing of o-nitrophenol, formaldehyde, and hydrazine, respectively. In another review paper, Liao et al. (pol.20230270) highlighted the latest advances of HCPs synthesized through classical synthesis approaches and morphological assembly methods for biological applications, ranging from drug delivery, antimicrobial, bioimaging, and biosensing. POPs incorporated various catalytic sites in the porous structures, and thus show strong catalytic properties. Huang et al. (pol.20230335) prepared polyhedral oligomeric silsesquioxane (POSS) and phosphonium-based ionic porous hypercrosslinked polymers, which can convert CO2 into highly value-added cyclic carbonates through heterogeneous catalytic addition reaction. Liu et al. (pol.20220638) prepared crown-ether-functionalized POPs (CE-POPs) through the Schiff-base condensation reaction and employed potassium-ion-bound POPs to synergistically catalyze the cycloaddition reaction of CO2 with epoxides to afford cyclic carbonates under mild and solvent-free conditions. In another two works, Liu et al. (pol.20230485) prepared porous C2N polymers, and Guo et al. (pol.20230263) prepared azo-bridged hydroxyl-rich pillar[5]arene-based porous organic polymers. These POPs show good performance in CO2 conversion to cyclic carbonates. Zhou et al. (pol.20230164) explored the synthesis of imine-linked and vinylene-linked COFs (different solvents: o-dichlorobenzene, 1,4-dioxane). The obtained COFs show different crystallinity and porosity from different solvents, and display photocatalytic performances in asymmetric α-alkylation of aldehydes. Furthermore, in the contribution by Zheng et al. (pol.20230362), through self-templated crystallization, hollowed covalent organic framework particles were obtained with tailored shell thickness and diameters and high crystallinity, and employed to support ethylene-oligomerization catalysts to improve the catalytic activity and selectivity to longer-chain α-olefins. POPs also contribute much to application in energy field. In three research articles, Tao et al. (pol.20220601) prepared microporous polycarbazole through ionothermal approach, Ejaz et al. (pol.20230174) prepared tetraphenylpyrazine-cored HCPs, Xu et al. (pol.20230256) hexaazatriphenyl-based POPs, and they employed these POPs in supercapacitors, which exhibit high specific capacitance. In another paper, Wang et al. (pol.20230759) extended π-conjugated hypercrosslinked polymers via Friedel–Crafts reaction and subsequent intramolecular Scholl-coupling reaction, and applied in LIBs. Last but not least, Zhou et al. (pol.20230273) summarized the progresses in COP-based thin films as memory devices. On the basis of synthesis and characterization of COP-thin films, they focus on the electronic properties and memory performances of 2D imine polymer-based memristors, 2D donor–acceptor COF-based memristors, and other 2D COF-based memristors. These contributions demonstrate the richness in the synthesis methodology, functionalization approach, and expanding application fields, however, which can reflect partial development of POPs. The POPs community will and wish to witness the more and more rapid evolution in the future. I would like to sincerely appreciate all the contributing authors for their work and time and gratefully thank the editors of J. Polym. Sci.