Since Jöns Jakob Berzelius coined the term “catalysis” in 1835 to describe the acceleration of reactions by substances that remain unchanged after the reaction, heterogeneous catalysis has played an increasingly more crucial role in the chemical industry and in domestic life. The Fe-catalyzed ammonia synthesis, a key step in the mass production of fertilizers from chemically inert N₂, led to one of the greatest changes in our world since the 1960s and 1970s, which was the so-called “Green Revolution”.¹  It is generally considered that the extra production of food significantly diminished food shortages and famine in Asian and Latin America. An estimated 40% of the world's population relies on chemical fertilizers to develop agricultural activities.²  Another successful example is the catalytic converter for fuel vehicles and stationary engines, which is used to reduce toxic exhaust gas pollutants such as CO, NO_x, hydrocarbons and small particles. In 1975, the catalytic converter was first introduced in the U.S. due to the strict regulation of exhaust emissions required by the U.S. Environmental Protection Agency. This has reduced the emission of pollutants by more than 10 billion tons in the U.S.³  Automotive catalysts have been regarded as one of the greatest engineering achievements of the 20th century.³  Clearly, any technical breakthrough in catalysis has a tremendous impact on the chemical industry, medicine, material science, and sustainable energy, which affects our society profoundly. During work spanning 100 years, scientists have found that the most reactive candidates for industrial catalysts are transition metals with variable oxidation states, like Fe, Co, Cu, V, Mo etc. What makes these transition metals serve as active catalysts is the ability to facilely lend out and store electrons once reactants adsorb and desorb from the surface of the catalysts, respectively. It suggests that non-metal elements, like the carbon group elements (C and Si), nitrogen group elements (N and P) and oxygen group elements (O and S), cannot act as efficient heterogeneous catalysts by themselves. During the last few decades, non-metal nanomaterials, mainly carbonaceous materials or carbon hybrids, have been intensively studied with respect to their unique structural complexities and resulting novel physicochemical properties, and have shown great potential in many fields like green energy, electronics, functional materials, medicine, and heterogeneous catalysis. It has been proved that the catalytic performance of supported metal active species can be greatly influenced by the chemical characteristics of the catalyst supports in reference to their surface functionalities. However, what was overlooked was that the flexibility of controlling electronic properties by modulating surface functionalities likely allowed reversible electron transfer between absorbents and the specific surface functionalities with the desired redox potential, which has been supported by both experimental data and DFT calculations.⁴  This means that non-metal inorganic materials can not only serve as unique catalyst supports, but also as catalysts themselves for various catalytic reactions. The potential application of these nanomaterials as metal-free catalysts will lead to a fundamental breakthrough in heterogeneous catalysis as basic concepts related with catalyst activation, surface chemisorption and other issues could be significantly expanded with respect to the novel catalytic functions of the nanomaterials. The mechanistic understanding of metal-free catalysis will subsequently facilitate industrial practice in the design and synthesis of fine-tunable catalysts with high efficiency and selectivity. Other advantages of metal-free catalysts include: (i) nanomaterials typically present a large surface area and high porosity with an abundance of surface functional groups; (ii) the microstructure can be adjusted to meet the requirements of different reactions; (iii) there are enormous physical forms with relative structural stability; (iv) surface functional groups can be easily regenerated; (v) the nanomaterials are environmentally benign, and disposal of the used catalysts will have a less negative impact on the environment; (vi) there is no subsurface involved in catalytic reactions, which will confine the scientific interest to quasi two-dimensional systems. However, the disadvantages of metal-free catalysts, in particular carbonaceous catalysts, also seriously limit their industrial applications with regards to their thermal instability and reproducibility. During the last few decades, the catalytic activities of carbon-based metal-free materials have attracted increasing attention in various fields, including catalytic oxidation, selective reduction, dehydration, electrocatalysis and so on.^5–9  In this chapter, we will summarize those contributions dedicated to exploring carbon-based materials as novel carbonaceous catalysts for the oxidative dehydrogenation (ODH) and direct dehydrogenation (DDH) of ethylbenzene and alkanes, as well as highlight the understanding of the chemical nature of metal-free catalysis. We expect the discussions will shed light on this new catalysis with great potential for green and sustainable synthetic chemistry.