Abstract
MOFs (metal-organic frameworks) significantly suffer from water- and heat instable issues, restricting their practical application, such as the capture of hazardous anionic dyes (e.g. Congo red, CR) from water. In the present contribution, a series of novel composites (UiO-67@CNTs) composed of microporous UiO-67 (Zr6O4(OH)4(CO2)12) and mesoporous CNTs (carbon nanotubes) have been innovatively synthesized by an in-situ hydrothermal reaction strategy. This UiO-67@CNT impressively retains structural integrity whether contacted with strong acid, distilled water, and strong alkali conditions even for 20 days. Due to the existence of CNT, its heat stability can reach up to 480 °C, which is superior to that of UiO-67. Open Zr(IV) sites, mesoporous, and high surface area in the structure of UiO-67@CNTs play associative effects for CR capture ability. CR uptakes over (5.0)UiO-67@CNTs can reach 1024 mg/g, exceeding some other previous adsorbents in literature. Importantly, UiO-67@CNTs could retain a remarkable CR capture ability even after the fifth cycle. This work expands views for water-heat resistant MOF-based composite with excellent ability of CR capture.
Highlights
CR (Scheme S1) is one of the typical anionic dye, which is usually considered as highly toxic and persistent to cause serious hazards for ecological environment and public health (Yagub et al 2014; Liu et al 2019)
UiO-67@CNTs achieved the purpose of pore expansion and improving the water resistant and hydrothermal stability, which was conducive to the adsorption of large size dye molecules such as CR, and we have investigated the CR adsorbed rate and controlling steps, and the kinetic and equilibrium parameters were presented and compared to support the results
While for (5.0)UiO-67@CNTs, there are a decrease of the surface area and an increase of the average pore size, attributing to existence of CNTs in its structure
Summary
CR (Scheme S1) is one of the typical anionic dye, which is usually considered as highly toxic and persistent to cause serious hazards for ecological environment and public health (Yagub et al 2014; Liu et al 2019). It is well known that the MOF consists of organic linkers and metal ions or clusters (Gao et al 2021; Uflyand et al 2021). Owing to their superiorities of uniform pore sizes, high specific surface areas, and flexible tailor-ability etc., MOF is often considered as an inspiring candidate for CR capture from wastewater (Sarker et al 2018; Wu et al 2021). Our group has investigated CR capture abilities by Cu-BTC or Zn/Cu-BTC@MC (Hu et al 2014; Sarker et al 2018). Compared with common sorbents (e.g. active carbon, and zeolite), Cu-BTC and Zn/ Cu-BTC@MC with cationic open sites exhibited excellent adsorptive abilities towards anionic CR
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