As the most promising next-generation lithium-ion battery anode materials, porous silicon-based materials are attracting great attention nowadays, mainly because of silicon's exceptionally high lithium storage capacity. However, how to realize the large-scale manufacture of these materials at low cost still remains a big challenge. In this work, we report the direct preparation of porous Si materials from metallurgical-grade Si in an autoclave, which is the most environmentally friendly route to produce alkoxysilane monomers in the organic silicon industry. In this reaction, Cu-based catalysts catalyze the reaction of Si particles with alcohols to create a porous structure within Si, followed by carbon deposition via the chemical vapor deposition method. The micro-morphology and -structure of the porous Si materials can be well tuned by adjusting the synthesis conditions. When used as the anode materials for lithium ion batteries, the charge capacity of the obtained porous Si/C materials was 1240 mA h g-1 at a current density of 50 mA g-1 after 50 cycles, much higher than that of the commercial graphite. This work provides an economic and scalable approach to the preparation of porous Si/C anode materials from commercial Si powders for lithium ion batteries.