Hierarchical porous MOF/CTF hybrid frameworks used as protection against acidic harmful gases

Abstract

Benefiting from the structural diversity, high porosity, controllable pore and functional design, porous organic frameworks (POPs) are attracting great attention in adsorption areas. In particular, metal–organic frameworks (MOFs) and covalent-organic frameworks (COFs) have exhibited fascinating potential in gas adsorption. However, in practical application, because the dominant micropores are unfavorable to the transport and diffusion of gas molecules, coupled with the unstable structure stemmed from weak coordination bonds, MOFs are restricted, while COFs are limited by the lack of sufficient active sites. The complementary advantages between MOFs and COFs provide ideas for designing novel hybrid frameworks. Here, a covalent triazine-based framework (CTF) was chosen as skeleton to in situ synthesize Zr-MOF-NH2, constructing an interpenetrated MOF/CTF hybrid. Further, Cu2+ ions were introduced to endow the hybrid with more active centers, resulting in a hierarchical porous Zr-MOF-NH2/CTF-Cu2+. The synergistic effect between MOF and CTF, coupled with Cu2+ active centers, endows the Zr-MOF-NH2/CTF-Cu2+ hybrid with exceptional adsorption performance for harmful acidic gases. The adsorption capacities of Zr-MOF-NH2/CTF-Cu2+ for SO2 and NO2 are 39.3 mg g−1 and 27.3 mg g−1, which are 2.6 and 3.1 times as high as that of Zr-MOF-NH2, respectively. Meanwhile, the breakthrough times of Zr-MOF-NH2/CTF-Cu2+ for SO2 and NO2 are 252.8 and 187.6 min, which are approximately 1.9 and 2.3 times as long as that of pristine MOF, respectively.