MOF–biochar composites for wastewater treatment: A review on synthesis, properties, and adsorption mechanisms

Industrial wastewater containing heavy metals, dyes, and emerging contaminants remains difficult to treat using conventional adsorbents due to limited selectivity and insufficient active sites. Recently, metal-organic framework-biochar (MOF–BC) composites have emerged as promising hybrid materials that combine the stability and low cost of biochar with the high porosity and tunable functionality of MOFs. This review summarizes recent advances in the design and application of MOF–BC composites for wastewater remediation. Key synthesis methods, including impregnation, in situ growth, mechanochemical synthesis, and hydrothermal approaches, are discussed in relation to their influence on structural and adsorption properties. The adsorption behavior of these materials toward major pollutant classes is analyzed, highlighting dominant mechanisms such as electrostatic interactions, coordination with metal sites, and pore diffusion. The influence of operational parameters, adsorption models, and recent advances in computational optimization are also discussed. In addition, challenges related to cost, scalability, and long-term stability are identified, along with future perspectives for practical implementation. The integration of artificial intelligence and response surface methodology is highlighted as a promising strategy for optimizing adsorption performance and process scalability. The review concludes that MOF-BC composites show significant potential as efficient and versatile adsorbents for advanced wastewater treatment applications.