Based on the increasing application requirements for the efficient adsorption of wastewater pollutants, graphene oxide-carbon nanotube/activated carbon (GO-CNT/AC) composites are constructed from the optimal microstructure matching of GO, CNTs, and AC materials by solution impregnation and freeze-drying methods. Three-dimensional structures with nano-micro hierarchical pores are established, with GO and CNTs uniformly dispersed on the AC surface, effectively restrain the agglomeration. The added CNTs played a “spring” role, supporting the gap between the GO sheets and AC matrix. Meanwhile, stable links are formed between GO, CNTs, and AC, realizing the synergistic matching of the microstructure, which provides abundant active absorption sites beneficial for improving the adsorption performance. The influences of the CNT contents, adsorbent amounts, methylene blue (MB) concentrations, and pH values on the adsorption property of GO-CNT/AC composites are systematically investigated. The results show that when the pH value of the MB solution is 13, the CNT concentration is 3 mg/mL and the MB concentration is 200 mg/L, the adsorption property of the composite is the best, with an adsorption capacity of 190.8 mg/g and a removal percentage of 95.4%. Compared with the raw AC, the adsorption capacity and removal percentage of the composites are increased by 73.9% and 72.8%, respectively. The GO-CNT/AC composites exhibit excellent cyclic adsorption performance, with a cyclic stability of 91.8% after six rounds of adsorption–desorption cycles. The kinetic analysis shows that the adsorption process conforms to the PSO kinetic model. By fitting of the IPD model, the adsorption mechanisms of the GO-CNT/AC composites are divided into two adsorption stages and described respectively. This study provides a new way to achieve highly efficient adsorption of pollutants in wastewater.

In view of the good adsorption properties of graphene and carbon foam, they were combined to achieve the optimal matching of microstructures. Taking mesophase pitch as a raw material, pitch-based carbon foam was prepared by the self-foaming method. Graphene gel was prepared as the second phase to composite with the carbon foam matrix; graphene-modified, pitch-based carbon foam composites were finally obtained. Graphene gel was dispersed in the rich pore structure of carbon foam to improve its agglomeration and the porosity, and the active sites of the composite were further increased; the adsorption properties and mechanical properties of the composites were also significantly improved. The microstructure and morphology of the composites were studied by SEM, XRD and Raman spectroscopy; the compressive property and porosity were also tested. Methylene blue (MB) solution was used to simulate a dye solution for the adsorption test, and the influence of the composite properties and MB solution on the adsorption property was studied. Results showed that the compressive strength of the composite was 13.5 MPa, increased by 53.41%, and the porosity was 58.14%, increased by 24.15%, when compared to raw carbon foam. When the mass of the adsorbent was 150 mg, the initial concentration of the MB solution was 5 mg/L, and the pH value of the MB solution was 11; the graphene-modified carbon foam composites showed the best adsorption effect, with an adsorption rate of 96.3% and an adsorption capacity of 144.45 mg/g. Compared with the raw carbon foam, the adsorption rate and adsorption capacity of the composites were increased by 158.18% and 93.50%, respectively.

Based on the large specific surface area and excellent adsorption potential of graphene quantum dots (GQDs) and zeolitic imidazolate framework-8 (ZIF-8) materials, a GQDs@ZIF-8 composite was constructed to achieve optimal matching of the microstructure and to acquire efficient adsorption of volatile organic compounds (VOCs). GQDs and ZIF-8 were synthesized and then compounded by the solution co-deposition method to obtain GQDs@ZIF-8 composites. GQDs were uniformly decorated on the surface of the ZIF-8 metal–organic framework (MOF), effectively restraining the agglomeration, improving the thermal stability of ZIF-8 and forming abundant active sites. Thus, the VOC removal percentage and adsorption capacity of the GQDs@ZIF-8 composites were significantly improved. Toluene and ethyl acetate were chosen as simulated VOC pollutants to test the adsorption performance of the composites. The results showed that, after the addition of GQDs, the adsorption property of GQDs@ZIF-8 composites for toluene and ethyl acetate was obviously improved, with maximum adsorption capacities of 552.31 mg/g and 1408.59 mg/g, respectively, and maximum removal percentages of 80.25% and 93.78%, respectively, revealing extremely high adsorption performance. Compared with raw ZIF-8, the maximum adsorption capacities of the composites for toluene and ethyl acetate were increased by 53.82 mg/g and 104.56 mg/g, respectively. The kinetics and isotherm study revealed that the adsorption processes were in accordance with the pseudo-first-order kinetic model and the Freundlich isotherm model. The thermodynamic results indicated that the adsorption process of the GQDs@ZIF-8 composites was a spontaneous, endothermic and entropy increase process. This study provides a new way to explore MOF-based adsorption materials with high adsorption capacity which have broad application prospects in VOC removal fields.