Site-selective etching and conversion of bismuth-based Metal–Organic frameworks by oxyanions enables efficient and selective adsorption via robust coordination bonding

The adsorption site-selective etching and conversion of CAU-17 microrods by Te and Se-containing oxyanions leads to the unprecedented hollow tubular and sponge-like structures via coordination bonding, which allows the selective and irreversible capture of the radiotoxic oxyanions from wastewater. [Display omitted] •The unique hollow tubular structure is obtained via etching of CAU-17 by TeOx2−.•SeO32− ions tend to etch CAU-17 into hierarchical sponge-like structures.•TeOx2− and SeO32− ions reacted with Bi-O bonds to form robust Bi-O-Te/Se bonds.•CAU-17 achieved the selective and irreversible capture of radiotoxic oxyanions. Anisotropic etching and conversion of MOF micro/nanostructures results in innovative structures and regulates properties. However, the anisotropic higher-order construction of MOFs remains a major challenge. Here, for the first time, we report the preparation of two unprecedented Bi-MOF (CAU-17) derivative structures via facile chemical etching and simultaneous conversion on solid CAU-17 microrods by reaction with Te- and Se-containing oxyanions. The TeOx2−-mediated hollow tubular structures are obtained via unique splitting, self-welding, and dissolution processes, a tube-forming mechanism never before seen in MOFs. In comparison, SeOx2− ions tend to etch CAU-17 into hierarchical sponge-like structures assembled from fine nanoparticles. DFT calculations, XANES modeling, and EXAFS fittings suggest that the site-selective coordination of oxyanions with Bi-O bonds in the Bi-MOF forms robust Bi-O-Te/Se bonds, which in turn leads to an anisotropic structural transition of CAU-17. More interestingly, benefiting from the coordination bond-dominated conversion, CAU-17 is shown to be a superior adsorbent for the selective and irreversible capture of highly radiotoxic oxyanions containing Te and Se from wastewater. These findings provide new insights into the anisotropic etching and conversion mechanism of MOFs by oxyanions and a fundamental understanding for designing advanced MOF-based guest oxyanion adsorbents.