## 5 Conclusions and Outlook  
It is one of the important tasks of sustainable development to rationally utilize existing energy and develop renewable energy instead of fossil energy. Biomass resources are considered important raw materials to replace fossil-based resources in the production of fuels and chemicals, and can be utilized reasonably on a large scale through catalysts with specific catalytic activities. As described above, POPs have established their position in the field of catalysis by virtue of their permanent pore structure, excellent stability, and low density structure, and they have also demonstrated their great potential in biomass utilization. The functional groups existing on the surface of POPs can provide reaction sites and have the potential to replace metal-based catalysis. At the same time, the stable structure also guarantees the recovery rate of the catalyst and saves costs. Their functionalization is not limited to one or some groups, but with the existing synthesis technology, achieving stable, uniform, and abundant active sites still needs more in-depth research. This paper mainly reviews the synthesis and the structural characteristics of POPs materials focused on the catalytic application of POPs as the main components of catalysts in lignocellulosic conversion to HMF and derivates. In the preparation of HMF by the catalytic dehydration of fructose and the preparation of follow-up chemicals by catalytic HMF, efficient production has not only been achieved through effective functionalization combined with the unique structure of the carrier materials but also through innovative synthesis methods to improve the inherent shortcomings of some POP materials, and their unique design takes into account the convenience of follow-up operations. In addition, the feasibility of the innovative application of some POPs materials is also discussed. POPs have been widely used in the field of catalysis and have good effects, but their potential has not been fully realized in the catalytic conversion of biomass studied in this paper. To be specific, they basically adopt thermal and electric catalytic systems. Although they have suitable structures for other catalytic systems, representative results in biomass conversion attempts have not yet been seen. We propose to make breakthroughs in the catalytic conversion of biomass using the design of the topological structure, the orderly regulation of the micro-morphology and the pore structure, and the directional loading of functional groups and active sites. In the practical application of natural resources in synthetic products, the one-step method can avoid the lengthy separation process and the purification process of intermediate compounds in subsequent processing. Cellulose can be converted into alcohol compounds, ester compounds, and organic acid compounds by homogeneous and heterogeneous catalytic systems in the one-pot method. However, POPs as a catalyst component have not been reported. In addition, almost all existing POP materials are synthesized under solvothermal conditions, and their requirements for synthesis environment and equipment make it hard to achieve large-scale synthesis. Although heterogeneous catalysis has improved the separation and purification efficiency of products, the applications of POPs in biomass conversion still face great challenges in separation and purification. We need to accurately extract each of the high-value chemicals from the resulting mixture to produce a product that meets the standards. Therefore, full use should be made of sustainable energy and technology combined with the structural characteristics of POP materials to continuously innovate and developing an efficient catalytic system so that it cannot only achieve the catalytic conversion into small molecules but also the direct conversion of biomass macromolecules into high-value chemicals.