## 1 Introduction  
Since their discovery at the end of the 20 th century, nanostructured carbon allotropes such as fullerenes [1; 2], carbon nanotubes [1; 3], carbon nanofibers [4], and graphene [5] have attracted the interest of several researchers from disparate fields. Nowadays, the family of low-dimensional carbon allotropes includes numerous members [6], supporting a wide range of applications from electronics [7] to medicine [8], from optics [9] to environment protection [10], from energy storage [11; 12; 13; 14] to catalysis [15]. While the synthesis strategies as well as the key structural features have already been extensively investigated, the focus has now shifted toward tuning the textural and electronic properties of these materials to optimize their performances in the pursuit of technological progress and manufacturing efficiency. Due to the nanometric sizes, the behavior of low-dimensional materials is dominated by surface phenomena; therefore, the design of carbon nanomaterials with tailored properties is essentially a matter of surface engineering. A common approach in surface engineering is functionalization, aiming to introduce a functional component that is able to confer novel properties to the material [16; 17]. In most cases, the surface functionalization results in the incorporation of heteroatoms (commonly boron, nitrogen, oxygen, phosphorus, and sulfur) in the carbon framework [18; 19; 20; 21]. Functional groups can be attached on the surface of carbon materialseither by non-covalent or covalent functionalization [22; 23]. In the former case, hydrogen bonding, \(\pi\)-cation, \(\pi\)-\(\pi\) stacking, \(\pi\)-anion electrostatic forces, hydrophobic interactions, and van der Waals forces are involved [24; 25]. Covalent functionalization implies the formation of stronger interactions, and often it is associated with structural alterations (defects) in the pristine carbon materials [26; 27; 28; 29]. Covalent bonds between carbon atoms and heteroatoms can be created during the synthesis (in situ doping) [30; 31] or by post-treatment of carbon materials (post-synthesis doping) [32]. Whatever the strategy used, the functionalization causes drastic changes in the electronic [33; 34], mechanical, and thermal [35] properties of carbon materials. For this reason, functionalized carbon materials have been successfully employed in catalysis. The introduction of heteroatoms generates defects that alter the surface structure and act as anchoring points for metal nanoparticles or active sites. Furthermore, it has been recently reported that the incorporation of heteroatoms (N, B, P, and S) in the framework of ordered mesoporous carbons can affect the d-spacing (and consequently the thickness of framework walls) and the pore texture of the resulting mesostructures, still maintaining well-defined porosity and moderate surface area [36]. In particular, N and S-doping lead to a slight pore size decrease, while B and P-doping produce an increase in the pore size, according to the different incorporation mechanisms, which can proceed, respectively, with the swelling of the carbon framework (N and S incorporation) or with the incorporation of oxygen, acting to etch the carbon (B and P-doping). In addition, heteroatom-doped carbon nanomaterials possess more pronounced acidic or basic [32] character compared to parent materials. Despite being promising metal-free catalysts [37; 38; 39], functionalized carbon materials represent suitable support for metal catalysts both in gas-phase and liquid-phase processes [40]. The modified local electron density and the presence of structural defects in the proximity of functionalities contribute to enhance the so-called metal-support interactions. The term strong metal-support interactions (SMSI) was coined by [PERSON] in 1978 in relation to the altered catalytic activity and chemisorptive properties of group VIII noble metals when supported on reducible oxides [41].