Networked Cages for Enhanced CO2 Capture and Sensing

Abstract It remains a great challenge to design and synthesize a porous material for CO2 capture and sensing simultaneously. Herein, strategy of “cage to frameworks” is demonstrated to synthesize fluorescent porous organic polymer (pTOC) by using tetraphenylethylene‐based oxacalixarene cage (TOC) as the monomer. The networked cages (pTOC) have improved porous properties, including Brunauer–Emmett–Teller surface area and CO2 capture compared with its monomer TOC, because the polymerization overcomes the window‐to‐arene packing modes of cages and turns on their pores. Moreover, pTOC displays prominent reversible fluorescence enhancement in the presence of CO2 in different dispersion systems and fluorescence recovery for CO2 release in the presence of NH3·H2O, and is thus very effective to detect and quantify the fractions of CO2 in a gaseous mixtures.

before analysis. H 2 isotherms were measured at 77 K up to 1.0 bar using a Micromeritics ASAP 2020 volumetric adsorption analyzer with the same degassing procedure. CO 2 isotherms were measured at 273 and 298 K up to 1.0 bar using a Micromeritics ASAP 2020 volumetric adsorption analyzer with the same degassing procedure.
Atomistic Simulations. Molecular models were generated from X-ray crystallographic data structure using Materials Studio 7.0 (Accelrys). Connolly surfaces were calculated by rolling a probe molecule across the substrate, the interface taken from the contact point of the probe molecule.

Synthesis of TPE based tricyclooxacalixarene cage TOC.
Scheme S1. Synthesis of TPE-based tricyclooxacalixarene cage TOC.
Anal. Calcd for C 72 H 36 Cl 8 N 4 O 8 : C,63.18;H,2.65;N,4.09;Found: C,63.43;H,2.98;N,4.33. Crystallographic data for TOC: Mr = 1368.65, Orthorhombic, Space group C 12/c1, a = 30.071 (7) and Bis(1,5-cyclooctadiene) nickel (481 mg, 1.75 mmol) were added to a 100 mL two-neck round bottom flask, followed by a solution of 1,5 -cyclooctadiene (189 mg, 1.75 mmol) in 30 mL DMF added by syringe. The combined mixture was stirred at 85 °C for 5 d before the reaction was allowed to cool down to RT, 40 mL 2M HCl was added into the reaction solution, stirred for 0.5 h, the precipitated polymer was collected by filtration and washed with a large amount of water, the products were successively washed with excess THF and CH 2 Cl 2 , and then sequentially purified by Soxhlet extraction with methanol, the purified products were dried in a vacuum oven at 60 °C for 12 h to obtain the final pTOC (140 mg, 88 %).
3. Variable-temperature 1 H NMR spectra of TOC.   6. X-ray crystal structures of TOC. Figure S4. The X-ray crystal structure of TOC from the side view (A) and two neighboring molecules of TOC pack in a window-to-arene mode (B) (part of no contacts atoms of one neighboring molecule of TOC were omitted for clarity).
12. Initial gas uptake slopes of TOC and pTOC at 273K.    19. The fluorescence spectrum of pTOC after bubbling CO2 and heating in water. Figure S18. The fluorescence spectra of pTOC after bubbling CO 2 and heating in water.