Ultrafine Ag Nanoparticles Encapsulated by Covalent Triazine Framework Nanosheets for CO₂ Conversion

Abstract

This paper describes the fabrication of covalent triazine framework nanosheet-encapsulated Ag nanoparticles (Ag0@CTFN) via a simple combination of the ultrasonic exfoliation and solution infiltration method. The as-prepared Ag0@CTFN displays an order layered-sheet structure with abundant micropores and mesopores, whereas ultrafine Ag nanoparticles are confined and stabilized in their interlayers through the interaction between N sites of triazine units and Ag nanoparticles. Considering that the Ag0@CTFN possesses the merits of high nitrogen, low density, and abundant basic sites, it was thus believed to have enough abilities to adsorb and activate CO2 in the CO2 conversion and catalysis. Importantly, the Ag0@CTFN, as a heterogeneous catalyst, showed highly catalytic activity in the carboxylation of various alkynes with CO2 at ambient pressure and low temperature. This catalyst also exhibited good functional group tolerance and excellent stability without any significant loss of its activity after six recycles. This work not only achieves valuable and novel composite material but also provides the first application of covalent triazine framework nanosheets in chemical conversion of CO2, opening a new field in preparing recyclable heterogeneous catalysts to accelerate the utilization of CO2.

Porous Carbon Nitride Frameworks Derived from Covalent Triazine Framework Anchored Ag Nanoparticles for Catalytic CO2 Conversion

“…CTF precursor is mainly prepared by the nucleophilic substitution of cyanuricc hloride and piperazine, according to our previous work. [20] It presentsa2D wrinkled sheet-like structure. Thereafter,P CNFs were obtainedb ythe direct carbonizationo f the CTF precursor under different pyrolysist emperatures.…”

“…The high-resolutionN1s spectrum of CTF precursor (Figure 3b)h as two types of nitrogen species, which correspond to piperazine NÀC( 397.3 eV) and triazine N=C( 398.6 eV) species. [20] However, all N1ss pectra of the PCNF-T materials can be deconvoluted into three newly formed types that contain pyridinic N( 397.9-398.0 eV), pyrrolic N( 399.9-400.5 eV), and graphitic N( 402.2-403.9 eV) species. [27] Notably,t he percentage of pyridinic Nd ecreased and pyrrolic Na toms increased with the increaseo f the pyrolysis temperature.…”

“…CTF precursor is mainly prepared by the nucleophilic substitution of cyanuric chloride and piperazine, according to our previous work . It presents a 2D wrinkled sheet‐like structure.…”

“…These results indicate the existence of graphitization carbon and the damage of the triazine ring in the CTF precursor, in accordance with FTIR and Raman results. The high‐resolution N 1s spectrum of CTF precursor (Figure b) has two types of nitrogen species, which correspond to piperazine N−C (397.3 eV) and triazine N=C (398.6 eV) species . However, all N 1s spectra of the PCNF‐ T materials can be deconvoluted into three newly formed types that contain pyridinic N (397.9–398.0 eV), pyrrolic N (399.9–400.5 eV), and graphitic N (402.2–403.9 eV) species .…”

“…The high-resolution C1 ss pectra (Figure 3a)s how three types of carbon species in the CTF precursor,w hich correspond to triazine NÀC=N( 283.6 eV), piperazine CÀCa nd CÀH( sp 3 ;2 84.8 eV), and piperazine CÀN( 286.7 eV) moieties. [20,25] As for the PCNF-T materials, an ew graphitic C species (288.6 eV) [26] appears together with the disappearance of the triazine NÀC=Nm oiety,a nd the piperazine Cs peciesi s still observed. These results indicate the existence of graphitization carbon and the damageo ft he triazine ring in the CTF precursor,i na ccordance with FTIR and Ramanr esults.…”