Jam City patched out hacked energy purchases a long time ago. As far as we're aware, G-Bo has no intention of finding another way to get around it. The only way to purchase energy with the gems cheat is to buy it through Brilliant Bargains (which, now, you can only do once per day instead of unlimited times).
Even so, be careful when purchasing energy. If you have more than 600, there's a flag that gets triggered on your account that causes JC to investigate you and there's a higher risk of getting banned. Any time you start to get close to 600 energy (because you'll inevitably get bonus energy through extra Chocolate Frog cards, story spree, etc.), turn off your infinite energy hack and play study sessions until you're back to 0.