Green and sustainable synthesis of nanostructured metal phosphates: structure-property relationships and catalytic applications.

Abstract

The sustainable design of effective catalysts necessitates synthetic methods that reduce resource usage while ensuring precise control over the composition, structure, and accessibility of active sites. Metal phosphates represent a versatile category of materials, as phosphate groups can directly engage in framework construction, influence the coordination and electronic environment of metal centers, and enhance acid-base, adsorption, and redox characteristics. This review thoroughly evaluates environmentally friendly and sustainable methods for synthesizing nanostructured metal phosphates, including hydrothermal, microwave-assisted, precipitation and co-precipitation, ultrasound-assisted, template-directed, mechanochemical, and solvent-free techniques. Instead of viewing individual studies as separate instances, the review analyzes how synthesis conditions affect nucleation, crystallization, morphology, porosity, defect formation, and multimetallic interactions, as well as how these structural attributes influence catalytic performance. Particular attention is devoted to the mechanistic role of phosphate species in material formation and catalysis, encompassing M-O-P bond formation, framework charge balance, template interactions, stabilization of metal centers, and modulation of Brønsted/Lewis acidity and redox behavior. The review critically assesses the advantages and limitations of nanoparticle, nanoporous, and hybrid architectures concerning active-site accessibility, mass transport, stability, leaching, and scalability. Finally, it highlights significant knowledge gaps, such as the identification of genuine active sites, operando structural evolution, quantitative structure-activity relationships, defect control, multimetallic synergy, and standardized sustainability evaluation. Thus, the review establishes a structure-mechanism-performance framework for the rational development of scalable and truly sustainable phosphate-based nanocatalysts.