1,3,5-Triazine-Based Microporous Polymers with Tunable Porosities for CO₂ Capture and Fluorescent Sensing

The synthetic control over pore structure remains highly desirable for porous organic frameworks. Here, we present a competitive chemistry strategy, i.e., a systematical regulation on Friedel–Crafts reaction and Scholl coupling reaction through tuning the ratios of monomers. This leads to a series of spirobifluorene-based microporous polymers (Sbf-TMPs) with systematically tuned porosities and N content. Unlike the existing copolymerization strategy by which the synthesized polymers exhibit a monotonic change tendency in the porosities, our networks demonstrate an unusually different trend where the porosity increases first and then decreases with the increasing Ph/Cl ratios for the monomers. This is mainly ascribed to the completion of coexisting reaction routines and the different “internal molecular free volumes” of the repeating units. The as-made networks feature tunable capacities for CO₂ adsorption over a wide range and attractive CO₂/N₂ selectivities. Moreover, these donor–acceptor type frameworks exhibit selective and highly sensitive fluorescence-on or fluorescence-off properties toward volatile organic compounds, which implies their great potential in fluorescent sensors

Facile Preparation of Dibenzoheterocycle-Functional Nanoporous Polymeric Networks with High Gas Uptake Capacities

A consolidated ionothermal strategy was developed for the polymerization of thermally unstable nitriles to construct high performance materials with permanent porosity, and carbazole, dibenzofuran, and dibenzothiophene were separately introduced into covalent triazine-based networks to investigate the effects of heterocycles on the gas adsorption performance. Three nitriles, namely 3,6-dicyanocarbazole, 3,6-dicyanodibenzofuran, and 3,6-dicyanodibenzothiophene, were designed and synthesized, which were readily converted to heat-resistant intermediates at a moderate temperature and then polymerized to create highly porous poly­(triazine) networks instead of the traditional one-step procedure. This documents an improved strategy for the successful construction of heterocyclic-functional triazine-based materials. The chemical structures of monomers and polymers were confirmed by ¹H NMR, FTIR, and elemental analysis. Such polymers with high physical–chemical stability and comparable BET surface areas can uptake 1.44 wt % H₂ at 77 K/1 bar and 14.0 wt % CO₂ at 273 K/1 bar and present a high selectivity for gas adsorption of CO₂ (CO₂/N₂ ideal selectivity up to 45 at 273<i>K</i>/1.0 bar). The nitrogen- and oxygen-rich characteristics of carbazole and dibenzofuran feature the networks strong affinity for CO₂ and thereby high CO₂ adsorption capacity. This also helps to thoroughly understand the influence of pore structure and chemical composition on the adsorption properties of small gas molecules

Facile Carbonization of Microporous Organic Polymers into Hierarchically Porous Carbons Targeted for Effective CO₂ Uptake at Low Pressures

The advent of microporous organic polymers (MOPs) has delivered great potential in gas storage and separation (CCS). However, the presence of only micropores in these polymers often imposes diffusion limitations, which has resulted in the low utilization of MOPs in CCS. Herein, facile chemical activation of the single microporous organic polymers (MOPs) resulted in a series of hierarchically porous carbons with hierarchically meso-microporous structures and high CO₂ uptake capacities at low pressures. The MOPs precursors (termed as MOP-7–10) with a simple narrow micropore structure obtained in this work possess moderate apparent BET surface areas ranging from 479 to 819 m² g^–1. By comparing different activating agents for the carbonization of these MOPs matrials, we found the optimized carbon matrials MOPs-C activated by KOH show unique hierarchically porous structures with a significant expansion of dominant pore size from micropores to mesopores, whereas their microporosity is also significantly improved, which was evidenced by a significant increase in the micropore volume (from 0.27 to 0.68 cm³ g^–1). This maybe related to the collapse and the structural rearrangement of the polymer farmeworks resulted from the activation of the activating agent KOH at high temperature. The as-made hierarchically porous carbons MOPs-C show an obvious increase in the BET surface area (from 819 to 1824 m² g^–1). And the unique hierarchically porous structures of MOPs-C significantly contributed to the enhancement of the CO₂ capture capacities, which are up to 214 mg g^–1 (at 273 K and 1 bar) and 52 mg g^–1 (at 273 K and 0.15 bar), superior to those of the most known MOPs and porous carbons. The high physicochemical stabilities and appropriate isosteric adsorption heats as well as high CO₂/N₂ ideal selectivities endow these hierarchically porous carbon materials great potential in gas sorption and separation