Thermal steam reduction etching to construct POM@CuICuII-BTC with hierarchical porosity for adsorption property enhancement

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2022-12, Vol.450, p.137966, Article 137966
• Main Authors: Cui, Yang, Shao, Zhichao, Zhao, Yujie, Geng, Kangshuai, Wen, Tianyang, Wu, Jie, Hou, Hongwei
• Format: Article
• Language: English
• Subjects: Adsorption; Hierarchical porosity; Metal-organic framework; Thermal steam reduction Etching; Tungstophosphoric acid
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2022.137966

[Display omitted] •Thermal steam reduction etching was first applied to prepare adsorbents.•TPA@CuICuII-BTC processes enlarged pores and exposed functional sites.•TPA@CuICuII-BTC exhibits excellent adsorption capacity and selectivity for Pb2+.•Mild modified strategy preserves the good reusability of TPA@CuICuII-BTC. Host MOFs with atomically precise characteristics and functional-oriented guest molecules are the key to assemble multifunctional host–guest MOF composites. We selected O−rich POM tungstophosphoric acid (TPA) and CuII-BTC with high stability and adjustable structure to synthesize host–guest TPA@CuII-BTC. Then thermal steam reduction etching was used to construct TPA@CuICuII-BTC with hierarchical pores at molecular scale, enlarging the pore space and making partially inaccessible sites of TPA@CuII-BTC more expose. Under the thermal methanol atmosphere, partial six-coordinated metal node Cu2+ was reduced slowly into Cu+ with lower coordination number, accompanied by the fracture of partial Cu−O coordination bonds. The generated TPA@CuICuII-BTC not only obtained larger pore and exposed more space in contrast to TPA@CuII-BTC, but also possessed more free hydroxyl oxygen sites due to the breaking of partial coordination bonds, promoting the contact and interaction of the composite with external substances. The Pb2+ adsorption experiment showed that TPA@CuICuII-BTC exhibited best adsorption ability to external Pb2+, and the adsorption capacity was 614.95 mg·g−1, which was 180.25 mg·g−1 and 243.45 mg·g−1 higher than that of TPA@CuII-BTC and CuII-BTC. This work has great reference significance for the construction of MOF composites with hierarchical porosity and the study of MOF composites on adsorption performance improvement.