Polyoxometalate-based covalent organic frameworks: The next generation of heterogeneous catalysts

Within the past 10 years, the rapid emergence of one subgroup of crystalline materials – polyoxometalate-based covalent organic frameworks (POMCOFs), composed of both inorganic polyoxometalates (POMs) molecular catalysts and organic building bricks – has uncovered their immense potential with regard to architectural versatility and potential application. However, work on synthesizing covalent organic frameworks (COFs) has thus far mostly been restricted to a number of conventional organic ligands; the development of porous crystalline POMCOFs as advantageous heterogeneous catalysts will be a promising pathway to catalyzing a variety of reactions more efficiently. Not only do these systems simultaneously offer the privileges of both homo- and heterogeneous catalysis, but they also allow a combination of unique recyclability and remarkable stability, along with adjustable selectivity. They can also promote electron transfer activity and the POMCOFs can sustain charge segregation of POMs. Concomitantly, these systems also display enhanced dispersion, elevated adsorption susceptibility, and ease of approach to the active sites. While earlier reviews have focused primarily on photocatalysis or photothermal catalysis, our review provides a broader perspective with particular emphasis on their design, synthesis, and diverse catalytic applications of POMCOFs. Therefore, we here summarize recent work on these valuable heterogeneous catalysts. This review affords an exhaustive description of the current development of porous POMCOFs, discusses their synthesis and classification, and examine their utilization, particularly in the area of catalysis.