China no longer sees Russia as a partner, but a vassal state. They rejected Putin's proposal for the Siberian pipeline and are slowing down deliveries of various components needed to manufacture weapons. Chinese banks are limiting their dealing with Russian banks and companies to avoid sanctions. Like it or hate it, US Dollar is the world's reserve currency and getting cut off from the global banking network is not worth all the gold that Putin can offer. China doesn't want Russia to attack other countries, because like a wise drug dealer, it does not want to loose its customers. Russia is killing them and that messes with China's business. To be honest if China could capture Putin and give him to the West in a box with a red ribbon it would. They saw how weak he is and have no respect for him.

On top of that, China has its own problems--demographic and economic. Russia cannot help China solve them so China is happy to see Russia bleed and slowly descend into the inevitable chaos once the Russian economy collapses. Xi will be happy to carve out a part of Russia for himself once an opportunity presents itself. Although how much more of a really backwards population and barren land he needs is a open question.