In this study, a novel solid dendrimer amine (hyperbranched polymers) was prepared using mesoporous carbon nitride functionalized by melamine based dendrimer amines. This adsorbent was denoted MDA-MCN-1. The process was stepwise synthesis and hard-templating method using mesoporous silica SBA-15 as a template. Cyanuric chloride and N,N-diisopropylethylamine (DIPEA, Merck) were used for functionalization of the MCN-1. Fourier transform infrared spectroscopy (FT-IR), Nitrogen adsorption-desorption analysis, Small Angle X-ray Scattering (SAXS), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were used for characterization of the adsorbent. This material was used for carbon dioxide gas (CO2) and methane gas (CH4) adsorption at high pressure (up to 20 bar) and room temperature. The volumetric method was used for the tests of the gas adsorption. The CO2 adsorption capacity of modified mesoporous carbon nitrides was about 4 mmol CO2 per g adsorbent. The methane adsorption capacity of this material was less than that CO2. Modified Mesoporous Carbon Nitride adsorbed about 3.52 mmol CH4 /g adsorbent. The increment of melamine based dendrimer generation on mesoporous surface increased adsorption capacity of both carbon dioxide and methane gases. According to the results obtained, the solid dendrimer amines, (MDA-MCN-1), performs excellently for CO2 and CH4 capture from flow gases and CO2 and CH4 storage.