Nanoporous Metal Phosphonate Hybrid Materials as a Novel Platform for Emerging Applications: A Critical Review

Nanoporous metal phosphonates are propelling the rapid development of emerging energy storage, catalysis, environmental intervention, and biology, the performances of which touch many fundamental aspects of portable electronics, convenient transportation, and sustainable energy conversion systems. Recent years have witnessed tremendous research breakthroughs in these fields in terms of the fascinating pore properties, the structural periodicity, and versatile skeletons of porous metal phosphonates. This review presents recent milestones of porous metal phosphonate research, from the diversified synthesis strategies for controllable pore structures, to several important applications including adsorption and separation, energy conversion and storage, heterogeneous catalysis, membrane engineering, and biomaterials. Highlights of porous structure design for metal phosphonates are described throughout the review and the current challenges and perspectives for future research in this field are discussed at the end. The aim is to provide some guidance for the rational preparation of porous metal phosphonate materials and promote further applications to meet the urgent demands in emerging applications.

Electronic Structure and Room Temperature Ferromagnetism in Gd-doped Cerium Oxide Nanoparticles for Hydrogen Generation via Photocatalytic Water Splitting

Enhanced visible light photocatalytic activity of Gd-doped CeO2 nanoparticles (NPs) is experimentally demonstrated, whereas there are very few reports on this mechanism with rare earth doping. All-pure and Gd-doped CeO2 NPs are synthesized using a coprecipitation method and characterized using X-ray diffraction (XRD), absorption spectroscopy, surface-enhanced Raman Spectroscopy (SERS), X-ray photoelectron spectroscopy (XPS), and superconducting quantum interference device (SQUID). The effect of Gd-doping on properties of CeO2 is discussed along with defects and oxygen vacancies generation. The XRD confirms the incorporation of Gd3+ at the Ce3+/Ce4+ site by keeping the crystal structure same. The average particle size from transmission electron microscopy (TEM) images is in the range of 5-7 nm. The XPS spectra of Ce 3d, O 1s, and Gd 4d exhibits the formation of oxygen vacancies to maintain the charge neutrality when Ce4+ changes to Ce3+. The gradual increase in hydrogen production is observed with increasing Gd concentration. The observed results are in good correlation with the characterization results and a mechanism of water splitting is proposed on the basis of analyses. The absorption spectra reveal optical band gap (2.5-2.7 eV) of samples, showing band gap narrowing leads to desired optical absorbance and photoactivity of NPs.